time: fix comment in test

The commit de36d1 (CL 4635083) changed the test time
from 2009 to 2010 but forgot to update the comment.

Change-Id: Ia2928773dd184f168fddde126d0bb936de8cfc29
GitHub-Last-Rev: bf8eb57140dc531d1af449308b79c646d3b64d02
GitHub-Pull-Request: golang/go#35930
Reviewed-on: https://go-review.googlesource.com/c/go/+/209517Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/time/format_test.go

@@ -119,7 +119,7 @@ var formatTests = []FormatTest{
 }
 
 func TestFormat(t *testing.T) {
-	// The numeric time represents Thu Feb  4 21:00:57.012345600 PST 2010
+	// The numeric time represents Thu Feb  4 21:00:57.012345600 PST 2009
 	time := Unix(0, 1233810057012345600)
 	for _, test := range formatTests {
 		result := time.Format(test.format)