fix: revert to IterableIterator type

StringIterator and MapIterator types are not exposed in TypeScript therefore invalid types

Author: musale

packages/abstractions/src/headers.ts

@@ -258,15 +258,15 @@ export class Headers extends Map<string, Set<string>> {
 	 * get keys of the headers collection
 	 * @returns an iterator of keys
 	 */
-	public keys(): StringIterator<string> {
+	public keys(): IterableIterator<string> {
 		return Object.keys(this.headers)[Symbol.iterator]();
 	}
 
 	/**
 	 * get entries
 	 * @returns an iterator of entries
 	 */
-	public entries(): MapIterator<[string, Set<string>]> {
+	public entries(): IterableIterator<[string, Set<string>]> {
 		return Object.entries(this.headers)[Symbol.iterator]();
 	}
 }