Chore: Fix import of Observable to be from rxjs and not rxjs/internal. It was maybe causing optimization bailouts

bookie/src/app/header-footer/header-footer.service.ts

@@ -1,6 +1,6 @@
 import { HttpClient, HttpHeaders } from '@angular/common/http';
 import { Injectable } from '@angular/core';
-import { Observable } from 'rxjs/internal/Observable';
+import { Observable } from 'rxjs';
 import { catchError } from 'rxjs/operators';
 
 import { ErrorLoggerService } from '../core/error-logger.service';