i18n: consistency tweaks

- Replace http by https
- Add Special:MyLanguage to MediaWiki.org URL

Spotted by Siebrand
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Semanticformsinputs-datepicker-dateformat/en
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Semanticformsinputs-desc/en

Change-Id: Iaeb66b877c924602f11cd768c915efda660c2c15