bug: revert "add trailing slash to the end of the url"

[WilliamBergamin]

This PR reverts #1594 in order to unblock potential future releases.

A potential bug was identified by @HTSagara in a comment on #1594. This was luckily brought up before a new version of the python-slack-sdk was released preventing users from being affected 💯 🥇

The changes introduced by #1594 are available in the issue-#1541 branch, please commit further changes to this branch 🙏

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.92%. Comparing base (c82c9a0) to head (0c91f8b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1597   +/-   ##
=======================================
  Coverage   84.92%   84.92%           
=======================================
  Files         113      113           
  Lines       12628    12622    -6     
=======================================
- Hits        10724    10719    -5     
+ Misses       1904     1903    -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests