Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/b6f6084a1202
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18082 from willyaranda/bug/993422

Bug 993422. Use a specific string for ActiveSync username

========

https://hg.mozilla.org/integration/gaia-central/rev/5291eaf5c332
Author: Guillermo López <gll@tid.es>
Desc: Bug 993422. Use a specific string for ActiveSync username

========

https://hg.mozilla.org/integration/gaia-central/rev/7a11c7123ed3
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18300 from guilherme-pg/bug983363

Bug 983363 - Remove debug IAC rule from Find My Device

========

https://hg.mozilla.org/integration/gaia-central/rev/aa706b987776
Author: Guilherme Goncalves <guilherme.p.gonc@gmail.com>
Desc: Bug 983363 - Remove debug IAC rules from Find My Device
Bumping manifests a=b2g-bump