Remove rails tests related to ApplyGitattributes gRPC

What does this MR do and why?

As part of the effort of removing reliance on info/attributes, we are making ApplyGitattributes gRPC as no-op (and will remove it later). See gitaly!6573 (merged) and gitaly#5348 (closed)

This MR aims to remove Rail tests related to ApplyGitattributes gRPC, so that tests will not fail when merging gitaly!6573 (merged)

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