Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/503c0dbb90d4
Author: Rudy Lu <me@rudy.lu>
Desc: Merge pull request #24738 from RudyLu/keyboard/Bug1077263-cleanup_altMenuMgr

Bug 1077263 - Remove "hasMovedAwayFromOriginalTarget" check in Alter…
r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/e9207d2e96c2
Author: Rudy Lu <me@rudy.lu>
Desc:  Bug 1077263 - Remove "hasMovedAwayFromOriginalTarget" check in AlternativesCharMenuManager.
Bumping manifests a=b2g-bump