test(dtslint): add dtslint test for sampleTime operator (#4093) (#4339)

* test(dtslint): add dtslint test for sampleTime operator (#4093)

* test(dtslint): remove dtslint test with repeated code (#4093)

spec-dtslint/operators/sampleTime-spec.ts

@@ -0,0 +1,14 @@
+import { of, asyncScheduler } from 'rxjs';
+import { sampleTime } from 'rxjs/operators';
+
+it('should enforce period parameter', () => {
+  const a = of(1, 2, 3).pipe(sampleTime()); // $ExpectError
+});
+
+it('should infer correctly', () => { 
+  const a = of(1, 2, 3).pipe(sampleTime(1000)); // $ExpectType Observable<number>
+});
+
+it('should accept scheduler parameter', () => {
+  const a = of(1, 2, 3).pipe(sampleTime(1000, asyncScheduler)); // $ExpectType Observable<number>
+});