Fix documentation

Author: wouterpeere

README.md

@@ -313,7 +313,7 @@ if you want more complex designs.
 import pygfunction as gt
 
 # set a rectangular borefield
-borefield_gt = gt.boreholes.rectangle_field(10, 12, 6, 6, 110, 1, 0.075)
+borefield_gt = gt.borefield.Borefield.rectangle_field(10, 12, 6, 6, 110, 1, 0.075)
 borefield.set_borefield(borefield_gt)
 ```
 

docs/sources/code/getting_started.md

@@ -233,7 +233,7 @@ if you want more complex designs.
 import pygfunction as gt
 
 # set a rectangular borefield
-borefield_gt = gt.boreholes.rectangle_field(10, 12, 6, 6, 110, 1, 0.075)
+borefield_gt = gt.borefield.Borefield.rectangle_field(10, 12, 6, 6, 110, 1, 0.075)
 borefield.set_borefield(borefield_gt)
 ```