build: update to angular-v9.1.12 (#1215)

Fixes: #1216

src/app/groups/groups-view/groups-view.component.ts

@@ -1,7 +1,7 @@
 /** Angular Imports */
 import { Component } from '@angular/core';
 import { ActivatedRoute, Router } from '@angular/router';
-import { MatDialog } from '@angular/material';
+import { MatDialog } from '@angular/material/dialog';
 
 /** Custom Dialogs */
 import { UnassignStaffDialogComponent } from './custom-dialogs/unassign-staff-dialog/unassign-staff-dialog.component';