[backport rh-test] remove checkbox from sign up form (#6271)

## Summary

Backport of #6269 to rh-test.

Removes the checkbox from the sign up form to simplify the user
experience.

## Changes

- Removed checkbox field from sign up schema
- Updated `SignUpForm.vue` component
- Kept rh-test-specific auth error display

## Conflict Resolution

Manually resolved merge conflict in `SignUpForm.vue`:
- Removed the checkbox as in main
- Preserved the auth error message section that exists on rh-test

The "By clicking 'Next' or 'Sign Up'..." notice already covers the same
information.

Original commit: b1439be7f0

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6271-backport-rh-test-remove-checkbox-from-sign-up-form-2976d73d36508109ba52eab1c80e787f)
by [Unito](https://www.unito.io)

src/schemas/signInSchema.ts

@@ -45,16 +45,11 @@ export const signUpSchema = passwordSchema
     email: z
       .string()
       .email(t('validation.invalidEmail'))
-      .min(1, t('validation.required')),
-    personalDataConsent: z.boolean()
+      .min(1, t('validation.required'))
   })
   .refine((data) => data.password === data.confirmPassword, {
     message: t('validation.password.match'),
     path: ['confirmPassword']
   })
-  .refine((data) => data.personalDataConsent === true, {
-    message: t('validation.personalDataConsentRequired'),
-    path: ['personalDataConsent']
-  })
 
 export type SignUpData = z.infer<typeof signUpSchema>