refactor: removed unused imports

web/src/app/app.component.ts

 import {Component} from '@angular/core';
 import {MatDialog, MatDialogConfig} from '@angular/material/dialog';
-import { Observable, of } from 'rxjs';
-import { mergeMap } from 'rxjs/operators';
 import {LogInDialogComponent} from './components/log-in-dialog/log-in-dialog.component';
 import {AuthServiceService} from './services/auth-service.service';