Fix save password form dialog on CI/CD Registration token

What does this MR do and why?

Fixes a bug where in Firefox the save password dialog appears when visiting the CI/CD project settings page.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Use Firefox with Ask to save logins and passwords for websites setting enabled
2. http://gdk.test:3000/flightjs/Flight/-/settings/ci_cd
3. Navigate to another page
4. Check functionality of Runners > Project runner registration token

Issue

The culprit is the Project runner registration token form in the dropdown as it switches the field from password to text depending it's state. When it's hidden it's a password which forces FF to believe it should show the save password dialog.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes #427896 (closed)
Related to #425468 (closed)

app/assets/javascripts/ci/runner/components/registration/registration_dropdown.vue

@@ -57,7 +57,6 @@ export default {
   data() {
     return {
       currentRegistrationToken: this.registrationToken,
-      showRegistrationToken: false,
     };
   },
   computed: {
@@ -101,16 +100,9 @@ export default {
     icon="ellipsis_v"
     text-sr-only
     no-caret
-    @shown="showRegistrationToken = true"
-    @hidden="showRegistrationToken = false"
   >
     <gl-dropdown-form class="gl-p-4!">
-      <registration-token
-        v-if="showRegistrationToken"
-        input-id="token-value"
-        :value="currentRegistrationToken"
-        @copy="onCopy"
-      >
+      <registration-token input-id="token-value" :value="currentRegistrationToken" @copy="onCopy">
         <template #label-description>
           <gl-icon name="warning" class="gl-text-orange-500" />
           <span class="gl-text-secondary">