chore(overlay): remove duplicate ComponentType interface (#8450)

* Removes a duplicated `ComponentType` interface from the `@angular/cdk/overlay`. The `ComponentType` interface should live in the portal entry point.

Author: devversion

src/cdk/overlay/generic-component-type.ts

@@ -23,7 +23,7 @@ import {
     throwUnknownPortalTypeError
 } from './portal-errors';
 
-
+/** Interface that can be used to generically type a class. */
 export interface ComponentType<T> {
   new (...args: any[]): T;
 }