kcms/rules: Remove custom executable to launch the rules KCM

Ismael Asensio requested to merge work/iasensio/remove-rulesdialog into master

The kwin_rules_dialog executable was used to launch the rules KCM on a specific window when called from the window menu because we couldn't depend on the kde-cli-tools repo

Since now kcmshell6 lives on KCMUtils we can call it directly

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