remove unused import

Author: chrishavlin

yt_idv/scene_components/blocks.py

@@ -6,7 +6,7 @@
 
 from yt_idv.gui_support import add_popup_help
 from yt_idv.opengl_support import TransferFunctionTexture
-from yt_idv.scene_components.base_component import SceneComponent, _cmaps
+from yt_idv.scene_components.base_component import SceneComponent
 from yt_idv.scene_data.block_collection import BlockCollection
 from yt_idv.shader_objects import component_shaders