ci: run on pull requests with slash in name

DifferentialOrange · DifferentialOrange · commit 61acda05fea7 · 2023-01-26T18:40:09.000+03:00
If branch name has slash in name, it didn't passes the `'*'` Github
Actions regexp.
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
@@ -2,7 +2,7 @@ name: Tests
 on:
   push:
     branches:
-     - '*'
+     - '**'
     paths-ignore:
      - 'doc/**'
 jobs:
