time: rename TestLoadLocationFromTzinfo to TestLoadLocationFromTZData

Tzinfo was replaced with TZData during the review of CL 68890, but this
instance was forgotten. Update it for consistency.

Follows CL 68890.
Updates #20629.

Change-Id: Id6d3c4f5f7572b01065f2db556db605452d1b570
Reviewed-on: https://go-review.googlesource.com/79176Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/time/zoneinfo_test.go

@@ -118,7 +118,7 @@ func TestLocationNames(t *testing.T) {
 	}
 }
 
-func TestLoadLocationFromTzinfo(t *testing.T) {
+func TestLoadLocationFromTZData(t *testing.T) {
 	time.ForceZipFileForTesting(true)
 	defer time.ForceZipFileForTesting(false)