Remove umd from exports

Our expectation is that if you're using the UMD builds, you're not
loading them through a normal module system like require or import.
Instead you're probably copying the files directly or loading them from
a CDN like unpkg.

Author: acdlite

packages/react-dom/package.json

@@ -50,7 +50,6 @@
     "./profiling": "./profiling.js",
     "./test-utils": "./test-utils.js",
     "./unstable_testing": "./unstable_testing.js",
-    "./umd/*": "./umd/*",
     "./src/*": "./src/*",
     "./package.json": "./package.json"
   },

packages/react/package.json

@@ -27,7 +27,6 @@
     "./package.json": "./package.json",
     "./jsx-runtime": "./jsx-runtime.js",
     "./jsx-dev-runtime": "./jsx-dev-runtime.js",
-    "./umd/*": "./umd/*",
     "./unstable-shared-subset": "./unstable-shared-subset.js"
 
   },