ci(actions) checkout v4 -> v5

See also: https://github.com/actions/checkout/releases/tag/v6.0.0

Author: tony

.github/workflows/tests.yml

@@ -13,7 +13,7 @@ jobs:
         python-version: ['3.14']
         tmux-version: ['2.6', '2.7', '2.8', '3.0a', '3.1b', '3.2a', '3.3a', '3.4', '3.5', 'master']
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install uv
         uses: astral-sh/setup-uv@v7
@@ -97,7 +97,7 @@ jobs:
         python-version: ['3.14']
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Install uv
         uses: astral-sh/setup-uv@v7