DOC fixes in contributing.rst
xref #15883
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15887?src=pr&el=h1) Report
> Merging [#15887](https://codecov.io/gh/pandas-dev/pandas/pull/15887?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/da0523a346abd9575ab05746e242ec67c1c442d4?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/15887/graphs/tree.svg?token=eZ4WkYLtcO&src=pr&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/15887?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #15887   +/-   ##
=======================================
  Coverage   90.97%   90.97%           
=======================================
  Files         145      145           
  Lines       49483    49483           
=======================================
  Hits        45015    45015           
  Misses       4468     4468
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.73% <ø> (ø)` | :arrow_up: |
| #single | `40.63% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15887?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/json/normalize.py](https://codecov.io/gh/pandas-dev/pandas/pull/15887?src=pr&el=tree#diff-cGFuZGFzL2lvL2pzb24vbm9ybWFsaXplLnB5) | `96.93% <ø> (ø)` | :arrow_up: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/15887?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.96% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15887?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/15887?src=pr&el=footer). Last update [da0523a...473f2cd](https://codecov.io/gh/pandas-dev/pandas/pull/15887?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments). thanks!