TST: IntervalTree.get_loc_interval should return platform int
One line change: missed this conversion in #23609
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23660?src=pr&el=h1) Report
> Merging [#23660](https://codecov.io/gh/pandas-dev/pandas/pull/23660?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/20bdb3e4019afe2037b26524a447ac8913d6e325?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23660/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23660?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #23660   +/-   ##
=======================================
  Coverage   92.24%   92.24%           
=======================================
  Files         161      161           
  Lines       51317    51317           
=======================================
  Hits        47338    47338           
  Misses       3979     3979
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.63% <ø> (ø)` | :arrow_up: |
| #single | `42.31% <ø> (ø)` | :arrow_up: |


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 thanks! https://travis-ci.org/MacPython/pandas-wheels/jobs/454816238 looks good in terms of interval related tests; the only failure now is #23605.  Not sure why the other job errored, but looks unrelated and I'd expect the output to be the same.