README.md: bump actions/checkout@v6

Node.js 20 actions are deprecated.

See-also: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
Signed-off-by: Florian Albrechtskirchinger <falbrechtskirchinger@gmail.com>
Closes: #22
Signed-off-by: Arthur Zamarin <arthurzam@gentoo.org>

Author: falbrechtskirchinger

README.md

@@ -48,7 +48,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Run pkgcheck
       uses: pkgcore/pkgcheck-action@v1
@@ -70,7 +70,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
 
     - name: Run pkgcheck
       uses: pkgcore/pkgcheck-action@v1