refactor: change remaining <template> to <ng-template> (#14706)

modules/@angular/common/src/directives/ng_plural.ts

@@ -21,9 +21,9 @@ import {SwitchView} from './ng_switch';
  * @howToUse
  * ```
  * <some-element [ngPlural]="value">
- *   <template ngPluralCase="=0">there is nothing</template>
- *   <template ngPluralCase="=1">there is one</template>
- *   <template ngPluralCase="few">there are a few</template>
+ *   <ng-template ngPluralCase="=0">there is nothing</ng-template>
+ *   <ng-template ngPluralCase="=1">there is one</ng-template>
+ *   <ng-template ngPluralCase="few">there are a few</ng-template>
  * </some-element>
  * ```
  *
@@ -89,8 +89,8 @@ export class NgPlural {
  * @howToUse
  * ```
  * <some-element [ngPlural]="value">
- *   <template ngPluralCase="=0">...</template>
- *   <template ngPluralCase="other">...</template>
+ *   <ng-template ngPluralCase="=0">...</ng-template>
+ *   <ng-template ngPluralCase="other">...</ng-template>
  * </some-element>
  *```
  *