ci: update 'actions/checkout' to v3

Update 'actions/checkout' version from 2 to 3 to address the Node 12
deprecation warning.

Signed-off-by: Victoria Dye <[email protected]>

Author: vdye

.github/workflows/main.yml

@@ -12,7 +12,7 @@ jobs:
         with:
           go-version: '1.19.0'
 
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
         with:
           path: src/git-bundle-server