Drop testing of 35.x branch

PiperOrigin-RevId: 971590429

.github/workflows/test_release_branches.yml

diff --git a/.github/workflows/test_release_branches.yml b/.github/workflows/test_release_branches.yml
index e29355b..d081d17 100644
--- a/.github/workflows/test_release_branches.yml
+++ b/.github/workflows/test_release_branches.yml
@@ -13,7 +13,7 @@
     strategy:
       fail-fast: false
       matrix:
-        branch: [25.x, 33.x, 35.x, 36.x]
+        branch: [25.x, 33.x, 36.x]
     runs-on: ubuntu-latest
     permissions:
       actions: write