Never hide file contents if they have comments.

Summary:
Links to comments were not working because file was hidden after it was deleted.

Test Plan:
Tested that comment anchors were working correctly for deleted files.
Tested that generated files were still hidden.

Reviewed By: epriestley
Reviewers: epriestley
CC: jungejason, aran, epriestley
Differential Revision: 257

src/applications/differential/parser/changeset/DifferentialChangesetParser.php

@@ -816,7 +816,7 @@ EOSYNTHETIC;
     }
 
     $shield = null;
-    if ($range_start === null && $range_len === null) {
+    if ($range_start === null && $range_len === null && !$this->comments) {
       if ($this->isGenerated()) {
         $shield = $this->renderShield(
           "This file contains generated code, which does not normally need ".