remove ref from checkout action

Author: saibatizoku

.github/workflows/ci-tests-n-coverage.yml

@@ -25,8 +25,6 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v3
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
 
       - uses: Swatinem/rust-cache@v2
         with:
@@ -98,8 +96,6 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v3
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
 
       - uses: Swatinem/rust-cache@v2
         with: