chore(oidc): graduate webkey to stable (#10122)

# Which Problems Are Solved

Stabilize the usage of webkeys.

# How the Problems Are Solved

- Remove all legacy signing key code from the OIDC API
- Remove the webkey feature flag from proto
- Remove the webkey feature flag from console
- Cleanup documentation

# Additional Changes

- Resolved some canonical header linter errors in OIDC
- Use the constant for `projections.lock` in the saml package.

# Additional Context

- Closes #10029
- After #10105
- After #10061

internal/api/oidc/access_token.go

@@ -53,7 +53,7 @@ func (s *Server) verifyAccessToken(ctx context.Context, tkn string) (_ *accessTo
 		tokenID, subject = split[0], split[1]
 	} else {
 		verifier := op.NewAccessTokenVerifier(op.IssuerFromContext(ctx), s.accessTokenKeySet,
-			op.WithSupportedAccessTokenSigningAlgorithms(supportedSigningAlgs(ctx)...),
+			op.WithSupportedAccessTokenSigningAlgorithms(supportedSigningAlgs()...),
 		)
 		claims, err := op.VerifyAccessToken[*oidc.AccessTokenClaims](ctx, tkn, verifier)
 		if err != nil {