action: fix smoke test for branch pattern

To match `master` and `stable/*` branches at least.

Signed-off-by: Yan Song <imeoer@linux.alibaba.com>

.github/workflows/smoke.yml

@@ -2,10 +2,10 @@ name: Smoke Test
 
 on:
   push:
-    branches: ["**"]
+    branches: ["**", "stable/**"]
     paths-ignore: [ '**.md', '**.png', '**.jpg', '**.svg', '**/docs/**' ]
-  pull_request:
-    branches: ["**"]
+  pull_request_target:
+    branches: ["**", "stable/**"]
     paths-ignore: [ '**.md', '**.png', '**.jpg', '**.svg', '**/docs/**' ]
   schedule:
     # Run daily sanity check at 03:00 clock UTC