Call MultipartForm.RemoveAll when request finishes (#19606)

modules/test/context_tests.go

@@ -38,6 +38,7 @@ func MockContext(t *testing.T, path string) *context.Context {
 		Resp:   context.NewResponse(resp),
 		Locale: &mockLocale{},
 	}
+	defer ctx.Close()
 
 	requestURL, err := url.Parse(path)
 	assert.NoError(t, err)