chore(combo): simplify CHANGELOG entry, reuse private method

Author: ViktorSlavov

CHANGELOG.md

@@ -94,7 +94,7 @@ All notable changes for each version of this project will be documented in this
         ...
         handleSelection(event: IComboSelectionChangeEventArgs) {
             const count = event.newSelection.length;
-            event.textValue = count > 0 ? `${count} friend${count > 1 ? 's' : ''} invited!` : `No friends invited :(`;
+            event.textValue = count > 0 ? `${count} friend(s) invited!` : `No friends invited :(`;
         }
         ...
     }

projects/igniteui-angular/src/lib/combo/combo.component.ts

@@ -1413,9 +1413,7 @@ export class IgxComboComponent extends DisplayDensityBase implements IgxComboBas
                     this.registerRemoteEntries(args.oldSelection, false);
                 }
             } else {
-                value = this.displayKey !== null && this.displayKey !== undefined ?
-                    this.convertKeysToItems(args.newSelection).map(entry => entry[this.displayKey]).join(', ') :
-                    args.newSelection.join(', ');
+                value = this.concatTextValue(args.newSelection);
             }
             this._value = value;
             this._onChangeCallback(args.newSelection);