remove geemap dependency

[iona5]

geemap pulls in an awful lot of dependencies. currently we use it only in the sentinel-2 download and preformat files:

• src\thaw_slump_segmentation\scripts\download_s2_4band_planet_format.py
• src\thaw_slump_segmentation\scripts\prepare_s2_4band_planet_format.py

which are as far as i can see superseded as this is done in thaw-slump-segmentation-pipeline and in branch sentinel2_native.

we should remove the geemap dependency once sentinel2 is stable to make packaging easier. if necessary functionality can be reproduced, as we use only download capabilities (uses geedim anyway) and data conversion from and to GeoDataFrame.

[initze]

    df = ee.data.computeFeatures({
        'expression': ftrCollection,
        'fileFormat': 'GEOPANDAS_GEODATAFRAME'
    })

[initze]

partially completed with #152