README.md: Clarify version number note

Signed-off-by: David A. Wheeler <dwheeler@dwheeler.com>

README.md

@@ -108,7 +108,7 @@ Create a .yml file under .github/workflows with the following contents:
 
 ```yml
 - name: flawfinder_scan
-  uses: david-a-wheeler/flawfinder@2.0.19-alpha1
+  uses: david-a-wheeler/flawfinder@2.0.19
   with:
     arguments: '--sarif ./'
     output: 'flawfinder_results.sarif'
@@ -117,6 +117,8 @@ Create a .yml file under .github/workflows with the following contents:
 You can add many other additions to the arguments.
 For example, `--error-level=4` will cause an error to be returned if
 flawfinder finds a vulnerability of level 4 or higher.
+Notice the version number after the `@` symbol; you can select a
+different version.
 
 You can find the action name and version string from [Marketplace](https://github.com/marketplace/actions/flawfinder_scan)
 by clicking "Use latest/xxx version" button.