Fix page not scrolling to the right section in the instructor help page.

src/web/app/pages-help/instructor-help-page/instructor-help-page.component.html

@@ -1,5 +1,5 @@
 <div class="flex-container">
-  <div class="main-body col-lg-10" #helpPage>
+  <div class="main-body col-lg-10">
     <div id={{Sections.body}}>
       <h1 class="color-orange"> Help for Instructors</h1>
       <div>

src/web/app/pages-help/instructor-help-page/instructor-help-page.component.ts

@@ -1,5 +1,5 @@
 import { DOCUMENT } from '@angular/common';
-import { AfterViewInit, Component, ElementRef, Inject, ViewChild } from '@angular/core';
+import { AfterViewInit, Component, Inject, ViewChild } from '@angular/core';
 import { ActivatedRoute, Params } from '@angular/router';
 import { PageScrollService } from 'ngx-page-scroll-core';
 import { environment } from '../../../environments/environment';
@@ -42,7 +42,6 @@ export class InstructorHelpPageComponent implements AfterViewInit {
   questionIdToExpand: string = '';
   section: string = '';
 
-  @ViewChild('helpPage') bodyRef ?: ElementRef;
   @ViewChild('studentsHelpSection') studentsHelpSection?: InstructorHelpStudentsSectionComponent;
   @ViewChild('coursesHelpSection') coursesHelpSection?: InstructorHelpCoursesSectionComponent;
   @ViewChild('sessionsHelpSection') sessionsHelpSection?: InstructorHelpSessionsSectionComponent;
@@ -104,13 +103,10 @@ export class InstructorHelpPageComponent implements AfterViewInit {
    * Scrolls to the section passed in
    */
   scroll(section: string): void {
-    if (this.bodyRef) {
-      const el: any = Array.prototype.slice
-          .call(this.bodyRef.nativeElement.childNodes).find((x: any) => x.id === section);
-      if (el) {
-        el.scrollIntoView();
-        window.scrollBy(0, -50);
-      }
+    const el: HTMLElement | null = this.document.getElementById(section);
+    if (el) {
+      const y: number = el.getBoundingClientRect().top + window.scrollY - 70;
+      window.scrollTo({ top: y, behavior: 'auto' });
     }
   }