Update README.md

Removed GitHub Action section from README.md.

README.md

@@ -82,27 +82,6 @@ cd gitleaks
 make build
 ```
 
-### GitHub Action
-
-Check out the official [Gitleaks GitHub Action](https://github.com/gitleaks/gitleaks-action)
-
-```
-name: gitleaks
-on: [pull_request, push, workflow_dispatch]
-jobs:
-  scan:
-    name: gitleaks
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
-      - uses: gitleaks/gitleaks-action@v2
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          GITLEAKS_LICENSE: ${{ secrets.GITLEAKS_LICENSE}} # Only required for Organizations, not personal accounts.
-```
-
 ### Pre-Commit
 
 1. Install pre-commit from https://pre-commit.com/#install