Update location of header P2PlusBubbleFunction.hpp in HyTeG

Following MR hyteg!887 the header file P2PlusBubbleFunction.hpp
no longer resides in experimental, but in p2functionspace.

hog/operator_generation/function_space_implementations/p2_plus_bubble_space_impl.py

@@ -121,7 +121,7 @@ class P2PlusBubbleFunctionSpaceImpl(FunctionSpaceImpl):
         return f"P2PlusBubbleFunction< {self.type_descriptor.pystencils_type} >"
 
     def includes(self) -> Set[str]:
-        return {f"hyteg/experimental/P2PlusBubbleFunction.hpp"}
+        return {f"hyteg/p2functionspace/P2PlusBubbleFunction.hpp"}
 
     def dof_transformation(
         self,