Fix oc-text-input keydown events

[kulmann]

When adding a @keydown event handler to the oc-text-input component, the handler gets fired multiple times.

Reproducible by creating an oc-text-input component, and adding a keydown.enter event, using the following handler:

onKeyDown() {
   console.log("test")
}

Observe, that each enter results in multiple events.

[kulmann]

Fixed by @LukasHirt in #768