Follow-up r58652: Add 'shared-repo-name-wikimediacommons' message which is used as...

Follow-up r58652: Add 'shared-repo-name-wikimediacommons' message which is used as $1 for 'sharedupload-desc-there' and friends when $wgUseInstantCommons is set to true.
Translations copied from 'shared-repo-name-shared' (extension WikimediaMessages)
This duplication can be deleted when $wgForeignFileRepos['name'] is changed to 'wikimediacommons' in CommonSettings.php. But to be fair I do not know if this would have any sideeffects.