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

========

https://hg.mozilla.org/integration/gaia-central/rev/71d2be782521
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Merge pull request #15950 from gtorodelvalle/contacts-967540-invalid-dates-in-gmail

Bug 967540 - [Contacts] Exporting to SD card contacts imported from Gmail with invalid dates never ends

========

https://hg.mozilla.org/integration/gaia-central/rev/7eac051011fe
Author: Germán Toro del Valle <gtorodelvalle@gmail.com>
Desc: Bug 967540 - [Contacts] Exporting to SD card contacts imported from Gmail with invalid dates never ends
Bumping manifests a=b2g-bump