i18n: consistency tweaks

Spotted by Siebrand
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Prefs-timezoneselector/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector-change/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector-change-setting/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector-notchange-temp/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector-pref-anon-desc/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector-pref-heading/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector-pref-message-short/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Timezoneselector-set-temp/en

Change-Id: I8838085b333609cd628455c67871983b396d8a59