remove cnp usage from sas.pyx
Building this particular file will no longer emit the numpy 1.7 deprecation warning.
FYI, there is a build bug currently, will be fixed when #22110 is pulled in. # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22111?src=pr&el=h1) Report
> Merging [#22111](https://codecov.io/gh/pandas-dev/pandas/pull/22111?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/0b7a08b70444056f964bb636a74ac41ca0058d37?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/22111/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22111?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22111   +/-   ##
=======================================
  Coverage   92.06%   92.06%           
=======================================
  Files         170      170           
  Lines       50705    50705           
=======================================
  Hits        46680    46680           
  Misses       4025     4025
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.47% <ø> (ø)` | :arrow_up: |
| #single | `42.31% <ø> (ø)` | :arrow_up: |


------

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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22111?src=pr&el=footer). Last update [0b7a08b...763ae49](https://codecov.io/gh/pandas-dev/pandas/pull/22111?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!