refactor(map): set generic type instead of any (#5118)

src/internal/operators/map.ts

@@ -79,7 +79,7 @@ class MapSubscriber<T, R> extends Subscriber<T> {
   // NOTE: This looks unoptimized, but it's actually purposefully NOT
   // using try/catch optimizations.
   protected _next(value: T) {
-    let result: any;
+    let result: R;
     try {
       result = this.project.call(this.thisArg, value, this.count++);
     } catch (err) {