Domains: Remove duplicated validation message in StateSelect

The problem was that in case of the text Input (when we don't have a
strict list of states for the given country), we've been showing the
`Input` component - which has its own `FormInputValidation`. This was
conflicting with the one in `StateSelect`. I've moved the one in
`StateSelect` so that it's only renendered when the `FormSelect`
implementation is used.

Fixes #12559

client/my-sites/upgrades/components/form/state-select.jsx

@@ -70,9 +70,9 @@ class StateSelect extends Component {
 								<option key={ state.code } value={ state.code }>{ state.name }</option>
 							) }
 						</FormSelect>
+						{ this.props.errorMessage && <FormInputValidation text={ this.props.errorMessage } isError /> }
 					</div>
 				}
-				{ this.props.errorMessage && <FormInputValidation text={ this.props.errorMessage } isError /> }
 			</div>
 		);
 	}