[BUGFIX lts] Revert container deprecation

We agreed that it was important to fix the error cases in #18717, but
while the work may be unnecessary, there isn't necessarily any
"correctness" issues with looking up things during destruction. Using
a deprecation to warn about potentially "unnecessary" work is a bit
heavy-handed, and at minimum requires some more continued discussions,
so reverting that part of the PR for now (while keeping the errors in
tact).

(cherry picked from commit b853324)

Author: chancancode

packages/@ember/-internals/container/lib/container.ts

@@ -1,7 +1,7 @@
 import { Factory, LookupOptions, Owner, OWNER, setOwner } from '@ember/-internals/owner';
 import { dictionary, HAS_NATIVE_PROXY } from '@ember/-internals/utils';
 import { EMBER_MODULE_UNIFICATION } from '@ember/canary-features';
-import { assert, deprecate } from '@ember/debug';
+import { assert } from '@ember/debug';
 import { assign } from '@ember/polyfills';
 import { DEBUG } from '@glimmer/env';
 import Registry, { DebugRegistry, Injection } from './registry';
@@ -584,14 +584,6 @@ class FactoryManager<T, C> {
       );
     }
 
-    if (DEBUG) {
-      deprecate(
-        `Instantiating a new instance of ${this.fullName} while the owner is being destroyed is deprecated.`,
-        !container.isDestroying,
-        { id: 'container.lookup-on-destroy', until: '3.20.0' }
-      );
-    }
-
     let injectionsCache = this.injections;
     if (injectionsCache === undefined) {
       let { injections, isDynamic } = injectionsFor(this.container, this.normalizedName);

packages/@ember/-internals/container/tests/container_test.js

@@ -736,75 +736,6 @@ moduleFor(
       assert.deepEqual(Object.keys(instance), []);
     }
 
-    '@test instantiating via container.lookup during destruction emits a deprecation'(assert) {
-      let registry = new Registry();
-      let container = registry.container();
-      class Service extends factory() {
-        destroy() {
-          expectDeprecation(() => {
-            container.lookup('service:other');
-          }, /Instantiating a new instance of service:other while the owner is being destroyed is deprecated/);
-        }
-      }
-      registry.register('service:foo', Service);
-      registry.register('service:other', factory());
-      let instance = container.lookup('service:foo');
-      assert.ok(instance, 'precond lookup successful');
-
-      runTask(() => {
-        container.destroy();
-        container.finalizeDestroy();
-      });
-    }
-
-    '@test instantiating via container.lookup during destruction enqueues destruction'(assert) {
-      let registry = new Registry();
-      let container = registry.container();
-      let otherInstance;
-      class Service extends factory() {
-        destroy() {
-          expectDeprecation(() => {
-            otherInstance = container.lookup('service:other');
-          }, /Instantiating a new instance of service:other while the owner is being destroyed is deprecated/);
-
-          assert.ok(otherInstance.isDestroyed, 'service:other was destroyed');
-        }
-      }
-      registry.register('service:foo', Service);
-      registry.register('service:other', factory());
-      let instance = container.lookup('service:foo');
-      assert.ok(instance, 'precond lookup successful');
-
-      runTask(() => {
-        container.destroy();
-        container.finalizeDestroy();
-      });
-    }
-
-    '@test instantiating via container.factoryFor().create() during destruction emits a deprecation'(
-      assert
-    ) {
-      let registry = new Registry();
-      let container = registry.container();
-      class Service extends factory() {
-        destroy() {
-          expectDeprecation(() => {
-            let Factory = container.factoryFor('service:other');
-            Factory.create();
-          }, /Instantiating a new instance of service:other while the owner is being destroyed is deprecated/);
-        }
-      }
-      registry.register('service:foo', Service);
-      registry.register('service:other', factory());
-      let instance = container.lookup('service:foo');
-      assert.ok(instance, 'precond lookup successful');
-
-      runTask(() => {
-        container.destroy();
-        container.finalizeDestroy();
-      });
-    }
-
     '@test instantiating via container.factoryFor().create() after destruction throws an error'(
       assert
     ) {