fix(ci): ubuntu-20.04 image is being phased out (#75)

Author: luau-project

.github/workflows/luacheck.yml

@@ -5,7 +5,7 @@ on: [ push, pull_request ]
 jobs:
 
   luacheck:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ "ubuntu-20.04", "macos-14", "windows-2025" ]
+        os: [ "ubuntu-24.04", "macos-14", "windows-2025" ]
         luaVersion: [ "5.4", "5.3", "5.2", "5.1", "luajit", "luajit-openresty" ]
     runs-on: ${{ matrix.os }}
     env: