chore: fix TypeScript latest breakage in CI (#6503)

* chore: appease TS in CI

global.gc seems to be possibly undefined in the latest Node types

* chore: appease TS

* chore: add optional shenanigans

Author: cartant

spec/Subscriber-spec.ts

@@ -244,7 +244,7 @@ describe('Subscriber', () => {
   });
 
   const FinalizationRegistry = (global as any).FinalizationRegistry;
-  if (FinalizationRegistry) {
+  if (FinalizationRegistry && global.gc) {
 
     it('should not leak the destination', (done) => {
       let observer: Observer<number> | undefined = {
@@ -262,7 +262,7 @@ describe('Subscriber', () => {
       const subscription = of(42).subscribe(observer);
 
       observer = undefined;
-      global.gc();
+      global.gc?.();
     });
 
   } else {

spec/operators/shareReplay-spec.ts

@@ -366,7 +366,7 @@ describe('shareReplay', () => {
   });
 
   const FinalizationRegistry = (global as any).FinalizationRegistry;
-  if (FinalizationRegistry) {
+  if (FinalizationRegistry && global.gc) {
     it('should not leak the subscriber for sync sources', (done) => {
       let callback: (() => void) | undefined = () => {
         /* noop */
@@ -382,7 +382,7 @@ describe('shareReplay', () => {
       shared.subscribe(callback);
 
       callback = undefined;
-      global.gc();
+      global.gc?.();
     });
   } else {
     console.warn(`No support for FinalizationRegistry in Node ${process.version}`);

spec/schedulers/intervalProvider-spec.ts

@@ -15,10 +15,10 @@ describe('intervalProvider', () => {
     let setCalled = false;
     let clearCalled = false;
 
-    global.setInterval = () => {
+    global.setInterval = (() => {
       setCalled = true;
       return 0 as any;
-    };
+    }) as any; // TypeScript complains about a __promisify__ property
     global.clearInterval = () => {
       clearCalled = true;
     };