docs: omit repetitions (#27746)

(cherry picked from commit 09433fb)

Author: aanchal88

src/cdk/a11y/interactivity-checker/interactivity-checker.ts

@@ -24,7 +24,7 @@ export class IsFocusableConfig {
 // supported.
 
 /**
- * Utility for checking the interactivity of an element, such as whether is is focusable or
+ * Utility for checking the interactivity of an element, such as whether it is focusable or
  * tabbable.
  */
 @Injectable({providedIn: 'root'})