Update GitHub workflows to latest checkout action

Author: josefs

.github/workflows/build-and-test.yml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         otp: ['25.3', '26.2', '27.2']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: erlef/setup-beam@v1
         with:
           otp-version: ${{matrix.otp}}

.github/workflows/proptests.yml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         otp: ['27.2']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: erlef/setup-beam@v1
         with:
           otp-version: ${{matrix.otp}}

.github/workflows/self-check.yml

@@ -15,7 +15,7 @@ jobs:
       matrix:
         otp: ['27.2']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: erlef/setup-beam@v1
         with:
           otp-version: ${{matrix.otp}}