Change username and password to max length of 256

Per comment from StackStorm/st2#5279, max
length of username for htpasswd and linux system can be up to 256.

Author: m4dcoder

modules/st2-login/login.component.js

@@ -219,7 +219,7 @@ export default class Login extends React.Component {
               placeholder="Username"
               required
               value={this.state.username}
-              maxLength="120"
+              maxLength="256"
               onChange={({ target: { value: username } }) => this.setState({ username })}
             />
           </LoginRow>
@@ -231,7 +231,7 @@ export default class Login extends React.Component {
               placeholder="Password"
               required
               value={this.state.password}
-              maxLength="120"
+              maxLength="256"
               onChange={({ target: { value: password } }) => this.setState({ password })}
             />
           </LoginRow>