migrations/github_test: fix updated timestamp for 1.6.0 milestone

Apparently TestGitHubDownloadRepo tests against live github data, and
today someone re-opened an old issue on the 1.6.0 milestone, bumping its
modify date and causing the test to fail.

modules/migrations/github_test.go

@@ -121,7 +121,7 @@ func TestGitHubDownloadRepo(t *testing.T) {
 		case "1.6.0":
 			assertMilestoneEqual(t, "1.6.0", "2018-09-25 07:00:00 +0000 UTC",
 				"2018-05-11 05:37:01 +0000 UTC",
-				"2019-01-27 19:21:22 +0000 UTC",
+				"2019-11-09 13:03:54 +0000 UTC",
 				"2018-11-23 13:23:16 +0000 UTC",
 				"closed", milestone)
 		case "1.7.0":