Fix scrollTo on Fabric (#4378)

## Summary

The flag `_IS_FABRIC` is only defined on React Runtime, we can't use
them on Reanimated Runtime. I removed the check of this flag for
Reanimated Runtime because this one prevents any `_dispatchCommand`
call.

## Test plan

Run any scrollTo example on Fabric

src/reanimated2/NativeMethods.ts

@@ -86,7 +86,7 @@ export function dispatchCommand(
   args: Array<unknown>
 ): void {
   'worklet';
-  if (!_WORKLET || !isNative || !global._IS_FABRIC) {
+  if (!_WORKLET || !isNative) {
     return;
   }