Punctuation and consistency for log-description-thanks

Added period and made consistent with core log descriptions.
<https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Log-description-thanks/en>

Change-Id: I7aaeecad6b662428bff9a2f4918a1943033f45d0
Merge "Punctuation and consistency for log-description-thanks"