Fix CI checkout after github new security policy

Github now fails with the following error when using
`on: pull_request_target`:
```
Error: Refusing to check out fork pull request code from a
'pull_request_target' workflow. This workflow runs with the base
repository's GITHUB_TOKEN, secrets, default-branch cache scope, and
runner access. Fetching and executing a fork's code in that trusted
context commonly leads to "pwn request" vulnerabilities. To opt in,
review the risks at https://gh.io/securely-using-pull_request_target and
set 'allow-unsafe-pr-checkout: true' on the actions/checkout step.
```

This reverts https://github.com/nvim-lua/kickstart.nvim/pull/571
and reopens https://github.com/nvim-lua/kickstart.nvim/pull/570

.github/workflows/stylua.yml

@@ -1,6 +1,10 @@
 # Check Lua Formatting
 name: Check Lua Formatting
-on: pull_request_target
+on:
+  push:
+    branches:
+      - master
+  pull_request:
 
 jobs:
   stylua-check:
@@ -10,8 +14,6 @@ jobs:
     steps:
       - name: Checkout Code
         uses: actions/checkout@v6
-        with:
-          ref: ${{ github.event.pull_request.head.sha }}
       - name: Stylua Check
         uses: JohnnyMorganz/stylua-action@v4
         with: