build: sync g3 change (#25845)

Adds a change that is present in g3, but not externally.

Author: crisbeto

src/cdk/testing/test-element.ts

@@ -21,6 +21,7 @@ export type EventData =
   | string
   | number
   | boolean
+  | Function
   | undefined
   | null
   | EventData[]

tools/public_api_guard/cdk/testing.md

@@ -76,7 +76,7 @@ export interface ElementDimensions {
 }
 
 // @public
-export type EventData = string | number | boolean | undefined | null | EventData[] | {
+export type EventData = string | number | boolean | Function | undefined | null | EventData[] | {
     [key: string]: EventData;
 };