Addresses review comments

Author: DrPaulSharp

RATapi/examples/normal_reflectivity/DSPC_function_background.py

@@ -145,7 +145,6 @@ def DSPC_function_background():
     problem.custom_files.append(
         name="D2O Background Function",
         filename="background_function.py",
-        function_name="backgroundFunction",
         language="python",
         path=pathlib.Path(__file__).parent.resolve(),
     )

RATapi/examples/normal_reflectivity/background_function.py

@@ -1,7 +1,7 @@
 import numpy as np
 
 
-def backgroundFunction(xdata, params):
+def background_function(xdata, params):
     # Split up the params array
     Ao = params[0]
     k = params[1]