Remove unused old logging messages for revision deletion

Per T20578, change a9c243b7b5289dad204278dbe7ed571fd914e395 (r97044)
has replaced these messages with a new set that doesn't rely on
"lego" concatenation. But the old messages were never removed.
Some were blacklisted on Translatewiki, but others continue to
waste translators' time.

The messages appear to not be used by any skins or extensions
in Wikimedia version control.

+--------------------------------+--------------------------------+
| Deleted old messages           | Replacements in current system |
+--------------------------------+--------------------------------+
| revdelete-logentry             | logentry-delete-revision       |
| revdelete-log-message          |                                |
+--------------------------------+--------------------------------+
| logdelete-logentry             | logentry-delete-event          |
| logdelete-log-message          |                                |
+--------------------------------+--------------------------------+
| revdelete-hid                  |  revdelete-content-hid         |
| revdelete-unhid                |  revdelete-content-unhid       |
|                                |  revdelete-summary-hid         |
| revdelete-content              |  revdelete-summary-unhid       |
| revdelete-summary              |  revdelete-uname-hid           |
| revdelete-uname                |  revdelete-uname-unhid         |
+--------------------------------+--------------------------------+

Change-Id: I27c616ca1aaca3058ad48753f5e4bfc64a71636e