minor #15862 unify expression: yarn run encore -> yarn encore (nabbisen)

This PR was submitted for the 5.4 branch but it was merged into the 4.4 branch instead.

Discussion
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unify expression: yarn run encore -> yarn encore

This commit unifies expression on yarn: `yarn run encore ...` -> `yarn encore ...` same to above in the same page.

Commits
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dd7e743 unify expression: yarn run encore -> yarn encore

Author: javiereguiluz

frontend/encore/simple-example.rst

@@ -268,7 +268,7 @@ and restart Encore:
 .. code-block:: terminal
 
     # if you use the Yarn package manager
-    $ yarn run encore dev --watch
+    $ yarn run dev --watch
 
     # if you use the npm package manager
     $ npm run watch