false positive on semgrep rule for RPC for workload identities

[tgross]

We'll need to update the rpc-potentially-unauthenticated rule to account for handling of workload identity-based auth, like we have in Secure Variables (example: https://github.com/hashicorp/nomad/actions/runs/2799623079/jobs/4414032548):

  nomad/secure_variables_endpoint.go 
     semgrep.rpc-potentially-unauthenticated
        RPC method structs.SecureVariablesApplyRPCMethod appears to be unauthenticated

         32┆ if done, err := sv.srv.forward(structs.SecureVariablesApplyRPCMethod, args, args, reply); done {
         33┆ 	return err
         34┆ }

(Opening an issue rather than just fixing it because I might not get a chance to hit this before I'm out next week.)