test: remove kokoro system tests for bigquery-storage

[danieljbruce]

Description

#8697 added the CI check to run bigquery-storage system tests in GCB so now we don't need to run the system tests in kokoro anymore. This pull request removes the CI check to run system tests from the kokoro environment because it is now redundant.

Impact

Removes redundant testing to save resources.

Files changed

• Removes the system-test.cfg files so that kokoro doesn't try to run system-test.sh from continuous or presubmit environments.
• Removes the system-test.sh file as it will not be used anymore now that the config files are gone
• trampoline_v2.sh example refers to samples-test.sh instead since system-test.sh doesn't exist anymore

[gemini-code-assist]

Code Review

This pull request removes Kokoro system test configuration files and the system-test.sh script, updating the OwlBot configuration to exclude the deleted script from template regeneration. The reviewer suggested also adding the deleted .cfg files to templates_excludes in owlbot.py to prevent OwlBot from regenerating them in future runs.

[gemini-code-assist]

Since you are removing the Kokoro system test configuration files (.kokoro/continuous/node18/system-test.cfg and .kokoro/presubmit/node18/system-test.cfg), they should also be added to templates_excludes to prevent OwlBot from regenerating them during the next run.

    templates_excludes=[
        'src/index.ts',
        'README.md',
        '.kokoro/system-test.sh',
        '.kokoro/continuous/node18/system-test.cfg',
        '.kokoro/presubmit/node18/system-test.cfg'
    ]

[danieljbruce]

I pushed an update to address this issue.

[pearigee]

Does owlbot actually generate these or are they entirely handwritten?

[danieljbruce]

I'm pretty sure system-test.sh is handwritten because it varies from library to library. It is probably okay to remove these from the excludes array.