Fix login type selector border

This fixes a regression in the login type selector's border and placement.

Fixes https://github.com/vector-im/riot-web/issues/10223

res/css/structures/auth/_Login.scss

@@ -83,11 +83,7 @@ limitations under the License.
 }
 
 .mx_Login_type_label {
-    flex-grow: 1;
-}
-
-.mx_Login_type_dropdown {
-    min-width: 200px;
+    flex: 1;
 }
 
 .mx_Login_underlinedServerName {

src/components/views/auth/PasswordLogin.js

@@ -312,7 +312,6 @@ export default class PasswordLogin extends React.Component {
                 <div className="mx_Login_type_container">
                     <label className="mx_Login_type_label">{ _t('Sign in with') }</label>
                     <Field
-                        className="mx_Login_type_dropdown"
                         id="mx_PasswordLogin_type"
                         element="select"
                         value={this.state.loginType}