.github: Bump actions/checkout from 3 to 4 (#69)

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Author: dependabot[bot]

.github/workflows/cross-illumos.yaml

@@ -17,7 +17,7 @@ jobs:
 
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 

.github/workflows/nshalman-sunos-releases.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Check out code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0