Remove bad "Session" link in User activity logs

Summary:
Fixes T12215. Two issues:

  - We build this `$session` link out of `$ip`, which is (a) wrong even if `$ip` was the IP and (b) super wrong since `$ip` is a tag.
  - These links don't work even if we'd built them right: searching by the //prefix// of a session identifier does nothing.

At least for now, just get rid of the links rather than trying to make this behavior work.

Test Plan:
On People > Activity logs:

  - Before patch: Saw bad links with bogus targets in "session" column.
  - After patch: Saw plain text in "session" column.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12215

Differential Revision: https://secure.phabricator.com/D17316

src/applications/people/view/PhabricatorUserLogView.php

@@ -43,12 +43,6 @@ final class PhabricatorUserLogView extends AphrontView {
             'href' => $base_uri.'?ip='.$ip.'#R',
           ),
           $ip);
-        $session = phutil_tag(
-          'a',
-          array(
-            'href' => $base_uri.'?sessions='.$ip.'#R',
-          ),
-          $session);
       }
 
       $action = $log->getAction();