chore(nimbus): Update Firefox Versions (#13491)

experimenter-github-app[bot] · Experimenter CircleCI Bot · web-flow · commit 5594c81cf313 · 2025-09-15T14:36:15.000Z
Co-authored-by: Experimenter CircleCI Bot &lt;experimenter-ci-bot@mozilla.com&gt;
diff --git a/experimenter/tests/firefox_fennec_release_build.env b/experimenter/tests/firefox_fennec_release_build.env
@@ -1,3 +1,3 @@
-FIREFOX_FENNEC_RELEASE_VERSION_ID="Firefox v142.0"
-BRANCH="fda95e1815322d9f1563d575bc1abb79d81041ab"
+FIREFOX_FENNEC_RELEASE_VERSION_ID="Firefox v143.0"
+BRANCH="6b1e8d6e411786bd05cbc8a278df529494e4b9fb"
 # Firefox version is "142.0.1"
