colocate original request-signature component styles (#9182)

Moves the styles out of the itcss folder and colocates them with the component, as per the pattern set elsewhere.

ui/app/components/app/index.scss

@@ -30,6 +30,7 @@
 @import '../ui/sender-to-recipient/index';
 @import '../ui/tabs/index';
 @import '../ui/token-balance/index';
+@import 'signature-request-original/index';
 @import 'token-cell/token-cell';
 @import 'transaction-activity-log/index';
 @import 'transaction-breakdown/index';

ui/app/css/itcss/components/index.scss

@@ -15,7 +15,6 @@
 @import './menu';
 @import './gas-slider';
 @import './simple-dropdown';
-@import './request-signature';
 @import './request-encryption-public-key';
 @import './request-decrypt-message';
 @import './pages/index';