Remove unnecessary conditional from example workflow snippet

Now that arduino/compile-sketches always generates a sketches report, the conditional in the workflow snippet in the readme is unnecessary. Although a user may decide they want to do advanced configuration of their workflow to control when the artifact is generated, there is no requirement that it only be made on pull_request events, so this only adds unnecessary complexity to the example.

The example should contain only the minimum necessary to effectively demonstrate the basic use of the action.

Author: per1234

README.md

@@ -176,8 +176,7 @@ Storing the sketches compilation report report as a [workflow artifact](https://
 - uses: arduino/compile-sketches@main
   with:
     enable-deltas-report: true
-- if: github.event_name == 'pull_request'
-  uses: actions/upload-artifact@v1
+- uses: actions/upload-artifact@v1
   with:
     name: size-deltas-reports
     path: size-deltas-reports