Update README.md

Update the commit SHA and tag after latest release

Author: varunsh-coder

README.md

@@ -46,7 +46,7 @@ Read this [case study](https://infosecwriteups.com/detecting-malware-packages-in
 
    ```yaml
    steps:
-     - uses: step-security/harden-runner@ebacdc22ef6c2cfb85ee5ded8f2e640f4c776dd5
+     - uses: step-security/harden-runner@18bf8ad2ca49c14cbb28b91346d626ccfb00c518 # v2.1.0
        with:
          egress-policy: audit
    ```