README-user.md: Add choices pkinit, hardened and idp to user_auth_type

The parameter user_auth_type has been updated in FreeIPA. The choices
pkinit, hardened and idp have been missing and are now added.

README-user.md

@@ -437,7 +437,7 @@ Variable | Description | Required
 `manager` | List of manager user names. | no
 `carlicense` | List of car licenses. | no
 `sshpubkey` \| `ipasshpubkey` | List of SSH public keys. | no
-`userauthtype` | List of supported user authentication types. Choices: `password`, `radius`, `otp` and ``. Use empty string to reset userauthtype to the initial value. | no
+`userauthtype` \| `ipauserauthtype` | List of supported user authentication types. Choices: `password`, `radius`, `otp`, `pkinit`, `hardened`, `idp` and `""`. An additional check ensures that only types can be used that are supported by the IPA version. Use empty string to reset userauthtype to the initial value. | no
 `userclass` | User category. (semantics placed on this attribute are for local interpretation). | no
 `radius` | RADIUS proxy configuration  | no
 `radiususer` | RADIUS proxy username | no