CI: Bump to NumPy compat to 1.9.3
1.9.2 doesn't seem to be available in `/pkgs/main`. We're seeing errors like

```
ImportError: libgfortran.so.1: cannot open shared object file: No such file or directory
```

when importing numpy.

Switching to 1.9.3 (which is available in main) solves that for me locally.
I'm not sure why appveyor wasn't run, but in theory it's unaffected by this.

Merging to get master passing again. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22499?src=pr&el=h1) Report
> Merging [#22499](https://codecov.io/gh/pandas-dev/pandas/pull/22499?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/447580e492271228c8e777757934ae5fd7af9515?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/22499/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22499?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22499   +/-   ##
=======================================
  Coverage   92.04%   92.04%           
=======================================
  Files         169      169           
  Lines       50776    50776           
=======================================
  Hits        46737    46737           
  Misses       4039     4039
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.45% <ø> (ø)` | :arrow_up: |
| #single | `42.23% <ø> (ø)` | :arrow_up: |


------

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