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

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https://hg.mozilla.org/integration/gaia-central/rev/25790d1036e0
Author: Fabien Cazenave <fabi1cazenave@users.noreply.github.com>
Desc: Merge pull request #32274 from Phoxygen/bug1210930-back-button-image-missing

Bug 1210930 - Back button image missing, r=albertopq

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https://hg.mozilla.org/integration/gaia-central/rev/9906848cc2f6
Author: Pierre-Eric Pelloux-Prayer <pierre-eric@phoxygen.com>
Desc: Bug 1210930 - Back button image missing

Dark theme images were forgotten during renaming of icons.
This is a followup of commit 688b18f9

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "5da94da9ea8d7712d95c9ced8476ae394d055495", 
+        "git_revision": "8ea9029190af2ffeb04dcd97b323738125e31a0e", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "17f80f95b26757f27ebf503d2358ed13a6308bc6", 
+    "revision": "25790d1036e01366a957eed0ade6c259f5442cbf", 
     "repo_path": "integration/gaia-central"
 }