Remove legacy web test results viewer

I just realized I had asked back in May whether anyone still uses
legacy-results.html, and nobody replied, so I think it's now safe
to remove this.

Context:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/9NFDSTEzcd4

Bug: 748628
Change-Id: I21e7d7451f3fa2e421daeb08e50a446e1e0a3253
Reviewed-on: https://chromium-review.googlesource.com/c/1355480
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
Reviewed-by: Aleks Totic <atotic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612458}

third_party/blink/tools/blinkpy/web_tests/controllers/manager.py

@@ -193,7 +193,6 @@ class Manager(object):
             self._upload_json_files()
 
             self._copy_results_html_file(self._results_directory, 'results.html')
-            self._copy_results_html_file(self._results_directory, 'legacy-results.html')
             if initial_results.keyboard_interrupted:
                 exit_code = exit_codes.INTERRUPTED_EXIT_STATUS
             else:

third_party/blink/web_tests/fast/harness/results.html

@@ -191,7 +191,6 @@ p, h2, h3, h4 {
 
 <div id="right-toolbar">
   <a id="help_button" href="javascript:GUI.toggleVisibility('help')">help</a>
-  <div style="">go back to <a href="legacy-results.html">legacy-results.html</a></div>
 </div>
 
 <div id="help" class="hidden hide-on-esc">