workflows: update to actions/checkout@v5 for node24 (#104)

No documented breaking changes.

Author: bgilbert

.github/workflows/codespell.yml

@@ -11,6 +11,6 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
       - name: Codespell
         uses: codespell-project/actions-codespell@v2

.github/workflows/run_unit_tests.yml

@@ -25,7 +25,7 @@ jobs:
           - os: windows-latest
             cc: cl
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v5
 
     - name: Install build and test dependencies (Linux)
       if: startsWith(matrix.os, 'ubuntu')