Update git submodules
- Update extensions/SecureLinkFixer from branch 'REL1_39' to e7567355c9435edb4affa9efd5670aa6f6ed70be
- build: Update MediaWiki requirement to 1.39.0
Change-Id: I3c67cb4fa9585ce036d41e8048814857a36065fe
- build: Update MediaWiki requirement to 1.39.0