beam_PostCommit_Java consistently timing out.

This seems to have first appeared with build #8367: https://ci-beam.apache.org/job/beam_PostCommit_Java/8367/

Frustratingly, no build scans pop up when the test fails this way, and no error messages appear except for the timeout. It may be easiest to attempt to determine which commit introduced the error.

The previous successful test is at commit b52762bf150cacceb0fdeb1f0dc85cbea6e6f39c

The first failing test is at commit 06a5e67332aae53ea90dedb4ef6421c2a7d65035