Bug : fix login signup and confirm tests to expect buttons disabled.

### **Describe the bug**

Currenlty, The tests expect that the signup login and change password buttons are enabled even when some fields are empty. However as discussed in the mentorship session the buttons should be disabled when the user has not filled up all the required fields.
**To Reproduce**

1. Run the existing ui tests.

### **Expected behavior**

Tests should take into account this behavior.

### **Additional context**

Self assigning as it should have been fixed in #1030 and has been discussed in the same pr. This was also discussed in the mentorship session.