DOC: remove the force uninstall from contributing guide (#27149)

Author: jorisvandenbossche

doc/source/development/contributing.rst

@@ -178,7 +178,6 @@ We'll now kick off a three-step process:
    # Create and activate the build environment
    conda env create -f environment.yml
    conda activate pandas-dev
-   conda uninstall --force pandas
 
    # or with older versions of Anaconda:
    source activate pandas-dev