chore(managed-identities): rm unused config API path

[zhumin8]

Removing unused API path from config for managed-identities, so that it matches the generated code status.

v1beta1 of java-managed-identities was added to the generation_config.yaml as part of initial migration to hermetic build: 14b7346, but client library code for v1beta1 is not present in java-managed-identities/google-cloud-managed-identities dir. This is due to deep-copy-regex being too strict and does not copy /v1beta1 from staging dir to final output.

Expect generation workflow to remove sample code related to v1beta1.

For #12736
For googleapis/librarian#5370

[gemini-code-assist]

Code Review

This pull request removes the v1beta1 proto path for the Managed Identities API from the generation configuration. I have no feedback to provide.

[zhumin8]

hmm, we got no changed libraries

+ changed_libraries=
+ echo 'Changed libraries are: No changed library.'
Changed libraries are: No changed library.