BUG: EWM silently failed float32
- [x] closes #42452
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

cc @mroeschke  Hi @jreback . Sorry I don't follow.
> we certainly don't support float16

Are you saying I should remove float16 here? 
`converted_dtypes.extend([np.float64, np.float32, np.float16])`


>this is not actually testing the result is correct

I have changed the earlier test (where I was just comparing the shape), to include constant data. I am comparing the result now(after @mroeschke suggested).



 @debnathshoham does this fix also close #41779 hi @simonjayhawkins,
I am getting the below right now (i.e. columns a with float16 is getting dropped)
```
      b     c     d     e     f
0   1.0   1.0   2.0   3.0   4.0
1   7.0   7.0   8.0   9.0  10.0
2  13.0  13.0  14.0  15.0  16.0
3  19.0  19.0  20.0  21.0  22.0
```

Adding float16 as well to the `converted_dtypes` list, would fix that as well. alternatively, i can see that just replacing with "number" below also fixes both (as suggested in the other BUG)
`obj = obj.select_dtypes(include=["integer", "float"], exclude=["timedelta"])` we are not supporting float16 in any way Hi @jreback, then this patch should work fine. Pls let me know if you think of any other changes I should make.  Thanks @debnathshoham 