Don't try to make WebSocket tests work in two environments

After struggling for a long while with trying to "shim" isomorphic-ws
to work normally in a jest environment, it is easier to just run this
test only in a Node environment.

Here are the issues why this test fails in JSDOM:

1. Imports fail

The statement `import WebSocket from 'isomorphic-ws';` is passed to the
Jest module resolver, which utilises `ts-jest-resolver` (in our case) to
find the right file to load. Sadly, it will always load the "main"
module of a node package.

2. isomorphic-ws "browser" option is ESM for some reason

If we use jest.config.cjs "resolver" field [1] to define a custom script,
we will be able to modify the "main" field by patching package.json in
memory. This works fine, however isomorphic-ws's browser version is an
ES Module for some reason, even if the package.json > "type" is
"commonjs".

3. Something inside jest doesn't want me to hack it to support ESM

If I override the package.json even harder to also change the "type" to
"module" just for isomorphic-ws, Jest doesn't respect it

4. ts-jest doesn't want to change the ESM imports to CJS imports

Since... we told it to not change ESM imports to CJS imports, it will
not.

[1]: https://jestjs.io/docs/configuration#resolver-string

Author: boxmein

test/unit/GraphQLSubscriptions.test.ts

@@ -1,4 +1,7 @@
 /* eslint-disable no-empty-function */
+/**
+ * @jest-environment node
+ */
 
 import { gql } from 'graphql-tag';
 import { filter, firstValueFrom, Subscriber } from 'rxjs';