Fix TLS helper test lint

Signed-off-by: Moritz Johner <beller.moritz@googlemail.com>

providers/v2/common/grpc/server/tls_test.go

@@ -55,7 +55,6 @@ func TestResolveCertPath(t *testing.T) {
 	}
 
 	for _, tt := range tests {
-		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()