Allow edit fields to custom credential types

The logic to disable certain fields is just valid for `encrypted`
fields. Since the multiline field - no secret, does not have a button to `replace`
the content to null  - it was always set to disabled.

Fix: https://github.com/ansible/awx/issues/10079

awx/ui_next/src/screens/Credential/shared/CredentialFormFields/CredentialField.jsx

@@ -106,6 +106,7 @@ function CredentialInput({ fieldOptions, credentialKind, ...rest }) {
         isLoading={fileIsUploading}
         allowEditingUploadedText
         validated={isValid ? 'default' : 'error'}
+        isDisabled={false}
       />
     );
   }