use Ubuntu slim instead of latest

Author: alxvth

.github/workflows/build.yml

@@ -15,7 +15,7 @@ env:
 # for matrix check https://docs.github.com/en/actions/reference/specifications-for-github-hosted-runners
 jobs:
   prepare_matrix:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     outputs:
       matrix: ${{ steps.matrix_setup.outputs.matrix }}
     steps: