[SPARK-20627][PYSPARK] Drop the hadoop distirbution name from the Python version

## What changes were proposed in this pull request?

Drop the hadoop distirbution name from the Python version (PEP440 - https://www.python.org/dev/peps/pep-0440/). We've been using the local version string to disambiguate between different hadoop versions packaged with PySpark, but PEP0440 states that local versions should not be used when publishing up-stream. Since we no longer make PySpark pip packages for different hadoop versions, we can simply drop the hadoop information. If at a later point we need to start publishing different hadoop versions we can look at make different packages or similar.

## How was this patch tested?

Ran `make-distribution` locally

Author: Holden Karau <holden@us.ibm.com>

Closes #17885 from holdenk/SPARK-20627-remove-pip-local-version-string.