Merge asof float fix
Fix bug with merge_asof when merging on floats and selecting a tolerance

- [ ] closes #22981 
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Hello @svenharris! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/reshape/merge.py`](https://github.com/svenharris/pandas/blob/322f965a43e312bc0a8df5c2fa46c7d0ad89f4d4/pandas/core/reshape/merge.py) !

 - There are no PEP8 issues in the file [`pandas/tests/reshape/merge/test_merge_asof.py`](https://github.com/svenharris/pandas/blob/322f965a43e312bc0a8df5c2fa46c7d0ad89f4d4/pandas/tests/reshape/merge/test_merge_asof.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22982?src=pr&el=h1) Report
> Merging [#22982](https://codecov.io/gh/pandas-dev/pandas/pull/22982?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/c282e310809921a0dadd4446f23c9273c15da443?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `50%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/22982/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22982?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #22982      +/-   ##
==========================================
- Coverage   92.18%   92.18%   -0.01%     
==========================================
  Files         169      169              
  Lines       50823    50828       +5     
==========================================
+ Hits        46853    46856       +3     
- Misses       3970     3972       +2
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.6% <50%> (-0.01%)` | :arrow_down: |
| #single | `42.36% <0%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/22982?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/22982/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `93.89% <50%> (-0.26%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22982?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22982?src=pr&el=footer). Last update [c282e31...928faaa](https://codecov.io/gh/pandas-dev/pandas/pull/22982?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 lgtm. @mroeschke merge when satisfied Thanks @svenharris 