Flaky validate-gradle-wrapper

What happened?

The validate-gradle-wrapper step in CI is flaky.

Consider:

https://github.com/pulumi/pulumi-java/runs/7235621044?check_suite_focus=true

  ✗ Found unknown Gradle Wrapper JAR files:
  e996d452d2645e70c01c11143ca2d3742734a28da2bf61f25c82bdc288c9e637 sdk/java/gradle/wrapper/gradle-wrapper.jar
  575098db54a998ff1c6770b352c3b16766c09848bee7555dab09afc34e8cf590 tests/examples/aws-java-pulumiup-platform/gradle/wrapper/gradle-wrapper.jar
  575098db54a998ff1c6770b352c3b16766c09848bee7555dab09afc34e8cf590 tests/integration/stack-reference/gradle/wrapper/gradle-wrapper.jar

Then rerun 2:

https://github.com/pulumi/pulumi-java/runs/7236878903?check_suite_focus=true

  ✓ Found known Gradle Wrapper JAR files: 
  e996d452d2645e70c01c11143ca2d3742734a28da2bf61f25c82bdc288c9e637 sdk/java/gradle/wrapper/gradle-wrapper.jar
  575098db54a998ff1c6770b352c3b16766c09848bee7555dab09afc34e8cf590 tests/examples/aws-java-pulumiup-platform/gradle/wrapper/gradle-wrapper.jar
  575098db54a998ff1c6770b352c3b16766c09848bee7555dab09afc34e8cf590 tests/integration/stack-reference/gradle/wrapper/gradle-wrapper.jar

I think we should possibly get rid of it, together with getting rid of gradle-wrapper.jar in the source, and instead trust the Gradle version installed in the GitHub Actions environment.

Steps to reproduce

See above

Expected Behavior

Consistent execution

Actual Behavior

Flaky execution

Versions used

No response

Additional context

No response

Contributing

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To contribute a fix for this issue, leave a comment (and link to your pull request, if you've opened one already).

Start by inspecting the validate-gradle-wrapper step in GitHub Actions and the Gradle wrapper files at sdk/java/gradle/wrapper/gradle-wrapper.jar, tests/examples/aws-java-pulumiup-platform/gradle/wrapper/gradle-wrapper.jar, and tests/integration/stack-reference/gradle/wrapper/gradle-wrapper.jar. Reproduce the check using the referenced CI runs, then verify that the wrapper validation executes consistently and that the intended source JAR cleanup is complete.