Remove /-/jwks endpoint

Problem

In %16.0 we removed the opt_in_jwt toggle from the codebase. The shared JWTs (CI_JOB_JWT, CI_JOB_JWT_V1, CI_JOB_JWT_V2) are still available in CI jobs unless they define ID tokens and will be removed in %17.0.

Proposal

Once we will remove those shared JWTs variables we can also get rid of our existing jwks endpoint.

• Remove /-/jwks endpoint which is an alias for /oauth/discovery/keys

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Feature Release Plan:

• Implement changes in %16.9 behind feature flag
• Enable the feature flag using chatops
• Remove the feature flag from code in %17.0