fix(validatable): don't validate if rules content hasn't changed
fix(validatable): don't validate if rules content hasn't changed

fixes #4688

Phlow2001/vuetify,Webifi/vuetify,vuetifyjs/vuetify,Phlow2001/vuetify,vuetifyjs/vuetify,Webifi/vuetify,vuetifyjs/vuetify,vuetifyjs/vuetify,Webifi/vuetify,Phlow2001/vuetify,Phlow2001/vuetify