Update git submodules

* Update Wikibase from branch 'master'
  to ec51ca0aec040b934b4c9f3b2e0ccdab00e78671
  - Merge "Bump stylelint-config-wikimedia from 0.13.1 to 0.14.0"
  - Bump stylelint-config-wikimedia from 0.13.1 to 0.14.0
    
    Bumps [stylelint-config-wikimedia](https://github.com/wikimedia/stylelint-config-wikimedia) from 0.13.1 to 0.14.0.
    - [Release notes](https://github.com/wikimedia/stylelint-config-wikimedia/releases)
    - [Changelog](https://github.com/wikimedia/stylelint-config-wikimedia/blob/master/CHANGELOG.md)
    - [Commits](wikimedia/stylelint-config-wikimedia@v0.13.1...v0.14.0)
    
    ---
    updated-dependencies:
    - dependency-name: stylelint-config-wikimedia
      dependency-type: direct:development
      update-type: version-update:semver-minor
    ...
    
    Signed-off-by: dependabot[bot] <[email protected]>
    Pull Request: wikimedia/mediawiki-extensions-Wikibase#372
    Change-Id: I64493e78fdc3911d2f5eabc15012ccb6535448a6