Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-1_4/rev/7c61051cfe7f
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #18445 from chuck-lee/bug-997791_Gaia_ui_test_error_on_wifi_enable_disable

Bug 997791 - Simulate echo setting to "wifi.enabled" from system app. r=arthurcc
Bumping manifests a=b2g-bump