TST: #14345 fixes TestDatetimeIndexOps test_nat AssertionErrors on 32-bit
- [ ] closes #14345 
     Changed tm.assert_numpy_array_equal(idx._nan_idxs, np.array([], dtype=np.int64)
     np.int64 to npintp
    All tests now pass on 32bit linux install.

## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/14347?src=pr) is 85.26% (diff: 100%)

> Merging [#14347](https://codecov.io/gh/pydata/pandas/pull/14347?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will increase coverage by **<.01%**

``` diff
@@             master     #14347   diff @@
==========================================
  Files           140        140          
  Lines         50632      50632          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43170      43171     +1   
+ Misses         7462       7461     -1   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [96b364a...73ad3d7](https://codecov.io/gh/pydata/pandas/compare/96b364a4a337b608c92dd6d5a00ceedd80c29315...73ad3d75a47ba4d7e938eb0614a4fc71da0cdc2f?src=pr)
 thanks @MattRijk lgtm.
