[DOCS] Bump Python, R, and Zeppelin versions to 1.9.1

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• No:
  • this is a documentation update. The PR name follows the format [DOCS] my subject

What changes were proposed in this PR?

Bump versions in preparation for the 1.9.1 release:

• python/sedona/version.py and python/pyproject.toml to 1.9.1
• R/DESCRIPTION to 1.9.1; R/R/dependencies.R to sedona-spark-shaded 1.9.1 and geotools-wrapper 1.9.1-33.5
• zeppelin/package.json and zeppelin/package-lock.json to 1.9.1
• mkdocs.yml: current_version 1.9.1, current_geotools 1.9.1-33.5, current_rc 1.9.1-rc1, current_git_tag sedona-1.9.1-rc1, current_snapshot 1.9.2-SNAPSHOT, next_version 1.9.2

How was this patch tested?

Version-string changes only; pre-commit hooks pass.

Did this PR include necessary documentation updates?

• No, this PR does not affect any public API so no need to change the documentation.