[DOCS] Update PyPI download badges in README

[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?

Replace the img.shields.io/pypi/dm/* monthly download badges with pepy.tech personalized badges for both apache-sedona and geospark in the download statistics table of README.md. The shields.io PyPI download badges have been unreliable; pepy.tech provides a stable equivalent that matches the styling already used for the "total downloads" badges in the same table.

How was this patch tested?

Visual inspection of the README markdown table. No code paths are affected.

Did this PR include necessary documentation updates?

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