src/app: fix path to deny-request-copy component

The themed-deny-request-copy.component erroneously includes the cus-
tom theme's deny-request-copy component instead of its own.

Closes: DSpace#2351

Author: alanorth

src/app/request-copy/deny-request-copy/themed-deny-request-copy.component.ts

@@ -1,7 +1,7 @@
 import { Component } from '@angular/core';
 import { ThemedComponent } from 'src/app/shared/theme-support/themed.component';
 
-import { DenyRequestCopyComponent } from 'src/themes/custom/app/request-copy/deny-request-copy/deny-request-copy.component';
+import { DenyRequestCopyComponent } from './deny-request-copy.component';
 
 /**
  * Themed wrapper for deny-request-copy.component