Build/Test Tools: Switch away from npx install-changed in GitHub Actions to increase the cache performance.

Using `npm ci` makes better use of the npm cache that's in use, speeding up the test runs by around 30 seconds.

See #52660


git-svn-id: https://develop.svn.wordpress.org/trunk@50446 602fd350-edb4-49c9-b593-d223f7449a82

.github/workflows/phpunit-tests.yml

@@ -133,7 +133,7 @@ jobs:
           key: ${{ runner.os }}-npm-${{ hashFiles('**/package-lock.json') }}
 
       - name: Install Dependencies
-        run: npx install-changed --install-command="npm ci"
+        run: npm ci
 
       - name: Get composer cache directory
         id: composer-cache