test: Mark `test_explorer_geo_revise_kind` with geo marker

[hoxbro]

Observed here: https://github.com/conda-forge/hvplot-feedstock/pull/30

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.94%. Comparing base (266565b) to head (881e2a3). Report is 7 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1426 +/- ## ========================================== + Coverage 88.91% 88.94% +0.02% ========================================== Files 51 52 +1 Lines 7651 7752 +101 ========================================== + Hits 6803 6895 +92 - Misses 848 857 +9 ```

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[maximlt]

cc @ahuang11