Update git submodules
- Update extensions/VisualEditor from branch 'REL1_39' to 20d7908705a5ead4fb33ab7654cbf7bcdf0cf091
- Localisation updates from https://translatewiki.net.
Change-Id: Ida56ef26f48081eccc034e608ea69da1c9fff6c9
- Localisation updates from https://translatewiki.net.