message: fix(aio): mark the 'titlecase' pipe as pure
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diff: // #docregion
  import { Pipe, PipeTransform } from '@angular/core';
  -@Pipe({name: 'titlecase', pure: false})
  +@Pipe({name: 'titlecase', pure: true})
  /** Transform to Title Case: uppercase the first letter of the words in a string.*/
  export class TitleCasePipe implements PipeTransform {
  transform(input: string): string {
  