Refactor output message

"/reflect/all_test.go : refactor message."

This PR corrects a syntax

%value -> %v

Change-Id: Ie56b93d238f090c564a88eb963dc9b7773054356
GitHub-Last-Rev: 023fde3ed4f31d5d702d76a593a63aaad1b4ac39
GitHub-Pull-Request: golang/go#66974
Reviewed-on: https://go-review.googlesource.com/c/go/+/580935
Reviewed-by: Joedian Reid <joedian@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
diff --git a/src/reflect/all_test.go b/src/reflect/all_test.go
index 5df83be..f2cb604 100644
--- a/src/reflect/all_test.go
+++ b/src/reflect/all_test.go
@@ -8521,7 +8521,7 @@
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
 			if !tc.testFunc(tc.value) {
-				t.Errorf("unexpected result for value.Clear(): %value", tc.value)
+				t.Errorf("unexpected result for value.Clear(): %v", tc.value)
 			}
 		})
 	}