chore: remove bindCallback workaround

src/internal/observable/bindCallback.ts

@@ -2,7 +2,6 @@
 import { SchedulerLike } from '../types';
 import { Observable } from '../Observable';
 import { bindCallbackInternals } from './bindCallbackInternals';
-import { TS_IncompatibleSignature } from '../util/workarounds';
 
 // tslint:disable:max-line-length
 /** @deprecated resultSelector is no longer supported, use a mapping function. */
@@ -142,7 +141,7 @@ export function bindCallback<A extends readonly unknown[], R extends readonly un
  * Observable that delivers the same values the callback would deliver.
  */
 export function bindCallback(
-  callbackFunc: TS_IncompatibleSignature,
+  callbackFunc: (...args: [...any[], (...res: any) => void]) => void,
   resultSelector?: ((...args: any[]) => any) | SchedulerLike,
   scheduler?: SchedulerLike
 ): (...args: any[]) => Observable<unknown> {

src/internal/observable/bindNodeCallback.ts

@@ -2,7 +2,6 @@
 import { Observable } from '../Observable';
 import { SchedulerLike } from '../types';
 import { bindCallbackInternals } from './bindCallbackInternals';
-import { TS_IncompatibleSignature } from '../util/workarounds';
 
 /** @deprecated resultSelector is deprecated, pipe to map instead */
 export function bindNodeCallback(
@@ -122,7 +121,7 @@ export function bindNodeCallback<A extends readonly unknown[], R extends readonl
  * deliver.
  */
 export function bindNodeCallback(
-  callbackFunc: TS_IncompatibleSignature,
+  callbackFunc: (...args: [...any[], (err: any, ...res: any) => void]) => void,
   resultSelector?: ((...args: any[]) => any) | SchedulerLike,
   scheduler?: SchedulerLike
 ): (...args: any[]) => Observable<any> {

src/internal/util/workarounds.ts

@@ -3,8 +3,3 @@
 // Wherever possible, use a TypeScript issue number in the type - something
 // like TS_18757 - or use a descriptive name and leave a detailed comment
 // alongside the type alias.
-
-// When TypeScript was bumped to version 4.2, there was an issue with
-// signatures being deemed incompatible when they ought to be compatible.
-// Really, any function should be compatible with `(...args: any[]) => void`.
-export type TS_IncompatibleSignature = any;