fix(ci): remove hardcoded branch filters from test-stats.yml trigger

Same structural fix as test-plugins.yml: drop the `branches` allowlist
so the Stats Plugin tests run on any branch/PR touching plugins/stats/
or the workflow file itself.

Author: erudenko

.github/workflows/test-stats.yml

@@ -2,12 +2,10 @@ name: Test Stats Plugin
 
 on:
   push:
-    branches: [main, fix/ci-type-errors-and-stale-test-date]
     paths:
       - 'plugins/stats/**'
       - '.github/workflows/test-stats.yml'
   pull_request:
-    branches: [main, fix/ci-type-errors-and-stale-test-date]
     paths:
       - 'plugins/stats/**'
       - '.github/workflows/test-stats.yml'