Update git submodules
- Update skins/Timeless from branch 'REL1_39' to 03050280ae0ec8d5e1a3b9b0fd4f35a7a427af53
- Merge "build: Update MediaWiki requirement to 1.39.0" into REL1_39
- build: Update MediaWiki requirement to 1.39.0
Change-Id: I64b0d5faee569827ca2ffb36eeb1006e3f6d70c4