Unify doc-strings (remove type/rtype)

As this information is already provided in type hints and we don't need to maintain it in two places.

src/ifcopenshell-python/ifcopenshell/api/project/assign_declaration.py

@@ -42,13 +42,10 @@ def assign_declaration(
     a declaration lets you say that an object belongs to a library.
 
     :param definitions: The list of objects you want to declare. Typically a list of assets.
-    :type definitions: list[ifcopenshell.entity_instance]
     :param relating_context: The IfcProject, or more commonly the
         IfcProjectLibrary that you want the object to be part of.
-    :type relating_context: ifcopenshell.entity_instance
     :return: The new IfcRelDeclares relationship or None if all definitions
         were already declared / do not support declaration.
-    :rtype: Union[ifcopenshell.entity_instance, None]
 
     Example:
 

src/ifcopenshell-python/ifcopenshell/api/project/unassign_declaration.py

@@ -32,12 +32,9 @@ def unassign_declaration(
 
     :param definitions: The list of objects you want to undeclare.
         Typically a list of assets.
-    :type definitions: list[ifcopenshell.entity_instance]
     :param relating_context: The IfcProject, or more commonly the
         IfcProjectLibrary that you want the object to no longer be part of.
-    :type relating_context: ifcopenshell.entity_instance
     :return: None
-    :rtype: None
 
     Example: