github: bump ubuntu runners to 24.04

20.04 is EOL soon.

.github/workflows/check.yml

@@ -65,7 +65,7 @@ jobs:
 
   snapshots:
     name: "🔍 Check for valid snapshot urls"
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - name: Check out code into the Go module directory
         uses: actions/checkout@v4
@@ -76,7 +76,7 @@ jobs:
 
   json-fmt:
     name: "🔍 Check JSON files for formatting consistency"
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - name: Install utils
         run: |