If your FeatureClass is in a geodatabase (file, mobile, enterprise, or memory), you can use this snippet to remove a field
https://github.com/Esri/arcgis-pro-sdk/wiki/ProSnippets-Geodatabase#removing-fields-from-a-table
Otherwise, you can use this code to use the GeoProcessing tool to remove a field.
var args = Geoprocessing.MakeValueArray(fcRamyPresahu, sloupce);
IGPResult result = await Geoprocessing.ExecuteToolAsync("management.DeleteField", args, null, null, null, GPExecuteToolFlags.None); //the last parameter does not add the result to the map
Read this page on more information about using GeoProcessing tools