docs(chore): make styles consistent for API doc headings

Closes #4816

modules/angular2/src/core/linker/dynamic_component_loader.ts

@@ -107,7 +107,7 @@ export abstract class DynamicComponentLoader {
    * Returns a promise for the {@link ComponentRef} representing the newly created Component.
    *
    *
-   * ## Example
+   * ### Example
    *
    * ```
    * @ng.Component({
@@ -167,7 +167,7 @@ export abstract class DynamicComponentLoader {
    * Returns a promise for the {@link ComponentRef} representing the newly created Component.
    *
    *
-   * ## Example
+   * ### Example
    *
    * ```
    * @ng.Component({
@@ -221,7 +221,7 @@ export abstract class DynamicComponentLoader {
    * Returns a promise for the {@link ComponentRef} representing the newly created Component.
    *
    *
-   * ## Example
+   * ### Example
    *
    * ```
    * @ng.Component({

modules/angular2/src/core/linker/view_manager.ts

@@ -76,7 +76,7 @@ export abstract class AppViewManager {
    * Use {@link AppViewManager#destroyRootHostView} to destroy the created Component and it's Host
    * View.
    *
-   * ## Example
+   * ### Example
    *
    * ```
    * @ng.Component({

modules/angular2/src/core/linker/view_ref.ts

@@ -43,7 +43,7 @@ export interface HostViewRef {
  * removing nested Views via a {@link ViewContainer}. Each View can contain many View Containers.
  * <!-- /TODO -->
  *
- * ## Example
+ * ### Example
  *
  * Given this template...
  *
@@ -139,7 +139,7 @@ export class ViewRef_ extends ViewRef {
  * {@link Compiler#compileInHost} API.
  *
  *
- * ## Example
+ * ### Example
  *
  * Given this template:
  *