chore(ci): remove legacy generate test

[noahdietz]

Removes the legacylibrarian Python container test for generate, which is no longer maintained or used.

The image build step is retained for build verification triggered by changes to the .generator/ directory. Unit tests otherwise cover the code therein.

[gemini-code-assist]

Code Review

This pull request simplifies the CI process by removing the library generation and building steps from cloudbuild-test.yaml, leaving only the generator image build verification. Additionally, two JSON metadata files for google-cloud-language were deleted. The reviewer suggests optimizing the build resources by reducing the timeout and machine type, and using the --no-push flag for Kaniko to avoid potential tag collisions during pull request builds.

[gemini-code-assist]

With the removal of the resource-intensive steps (cloning googleapis, generating, and building the library), the global timeout of 7200s (line 17) and the E2_HIGHCPU_32 machine type (line 37) are now likely excessive for a single image build verification. Consider reducing these values to optimize resource usage and ensure faster failure feedback. Additionally, if this build is triggered by pull requests, pushing to the registry as mentioned in the comment can lead to tag collisions; consider using the --no-push flag in the Kaniko arguments if the goal is strictly build verification.