DOC: Force Removal of pandas From Dependencies
From a discussion on Gitter with @TomAugspurger when following the pandas contributing guide the step:

```sh
conda env create -f environment.yml
```

Causes pandas to be installed in the environment from conda as a result of dependency resolution with third party libraries (ex: statsmodels, pyarrow, seaborn). 

To prevent undesired conflicts between the local development version and the installed version we should update the documentation to have an explicit removal of the bundled version as such:

```sh
conda uninstall --force pandas
```