gha: bump setup to v4

Author: joemiller

.github/workflows/ci.yaml

@@ -19,7 +19,7 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: actions/setup-go@v4
         with:
@@ -41,7 +41,7 @@ jobs:
     if: github.ref != 'refs/heads/main'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - uses: actions/setup-go@v4
         with:
@@ -63,7 +63,7 @@ jobs:
     # only create a release on main builds:
     steps:
       - name: checkout code with full history (unshallow)
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0