Allow typing magic links on mobile

When typing a magic link, rather than pasting it, iOS seems to send
`keydown.enter`, and we weren't submitting the form in that case.

Changed to submit the form in either case, and use the state of the
input target to help guard against double submissions.

app/javascript/controllers/magic_link_controller.js

@@ -4,16 +4,12 @@ import { onNextEventLoopTick } from "helpers/timing_helpers"
 export default class extends Controller {
   static targets = [ "input" ]
 
-  submit(event) {
+  submit() {
     onNextEventLoopTick(() => {
-      this.inputTarget.disabled = true
-    })
-  }
-
-  paste(event) {
-    onNextEventLoopTick(() => {
-      this.element.submit()
-      this.inputTarget.disabled = true
+      if (!this.inputTarget.disabled) {
+        this.element.submit()
+        this.inputTarget.disabled = true
+      }
     })
   }
 }