Use ' instead of curved one for consistency

Spotted by Shirayuki in
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Donate_interface-cvv-explain/en_etc.
(the period is part of the URL).

Change-Id: Ie43a074294149be40e67d3d01cc0c445f92e7ba3
Merge "Use ' instead of curved one for consistency"