ci: disable i386-unknown-linux-gnu

Disable i386 linux build for ubuntu-24.04, due to
actions/runner-images#9977

.github/workflows/stable.yml

@@ -175,7 +175,8 @@ jobs:
     runs-on: ubuntu-24.04
     strategy:
       matrix:
-        target: ["aarch64-unknown-linux-gnu","armv7-unknown-linux-gnueabihf","i686-unknown-linux-gnu"]
+        # "i686-unknown-linux-gnu" is disabled in ubuntu24.04 runner
+        target: ["aarch64-unknown-linux-gnu","armv7-unknown-linux-gnueabihf"]
     # Only run on "pull_request" event for external PRs. This is to avoid
     # duplicate builds for PRs created from internal branches.
     if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name != github.repository