Remove unnecessary copies of loop variables (#28138)

server/channels/web/params_test.go

@@ -480,7 +480,6 @@ func TestParamsFromRequest(t *testing.T) {
 	}
 
 	for _, testCase := range testCases {
-		testCase := testCase
 		t.Run(testCase.Description, func(t *testing.T) {
 			t.Parallel()