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

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https://hg.mozilla.org/integration/gaia-central/rev/2aa6df93d4d5
Author: Greg Weng <snowmantw@gmail.com>
Desc: Merge pull request #20030 from kamituel/Bug_1020549_invalid_use_of_let

Bug 1020549: Replace 'let' with 'var'.

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https://hg.mozilla.org/integration/gaia-central/rev/9d526ef53cad
Author: Kamil Leszczuk <kamituel@gmail.com>
Desc: Bug 1020549: Replace 'let' with 'var'.

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https://hg.mozilla.org/integration/gaia-central/rev/09332b1b3846
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #19923 from pivanov/bug-1019197

Bug 1019197 - [Flame] Spinners are broken

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https://hg.mozilla.org/integration/gaia-central/rev/ab2c7785f58a
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 1019197 - [Flame] Spinners are broken
Bumping manifests a=b2g-bump