UI: rename "OpenGL" render engine to "Workbench".

Neither is very descriptive for its task, but at least workbench is more
future proof and distinguishes it from Eevee.

release/scripts/startup/bl_ui/properties_data_bone.py

@@ -401,7 +401,7 @@ class BONE_PT_deform(BoneButtonsPanel, Panel):
 
 
 class BONE_PT_custom_props(BoneButtonsPanel, PropertyPanel, Panel):
-    COMPAT_ENGINES = {'BLENDER_RENDER', 'BLENDER_EEVEE', 'BLENDER_OPENGL'}
+    COMPAT_ENGINES = {'BLENDER_RENDER', 'BLENDER_EEVEE', 'BLENDER_WORKBENCH'}
     _property_type = bpy.types.Bone, bpy.types.EditBone, bpy.types.PoseBone
 
     @property