[Gpr_To_Absl_Logging] Removing deprecated code.

1.  Function gpr_set_log_verbosity has been deprecated. This function will be deleted in a few weeks.
1.  gRPC now internally uses absl logging. Earlier gRPC was using its own custom logging mechanism called gpr which had a whole set of functions beginning with gpr_.
1.  This entire unit test is being re-written as a part of another PR. But that PR will take a while to merge. In the mean team I want to delete all instances of this function to prevent further backsliding.
https://github.com/grpc/grpc/pull/37177

PiperOrigin-RevId: 654639955

test/core/end2end/tests/no_logging.cc

@@ -62,7 +62,6 @@ class Verifier {
     // This is broken. Replace with an absl log sink.
     gpr_set_log_function(gpr_default_log);
     saved_trace_flags_.Restore();
-    gpr_set_log_verbosity(saved_severity_);
   }
   Verifier(const Verifier&) = delete;
   Verifier& operator=(const Verifier&) = delete;