[DOC] reflect change in function name

Author: balbasty

cornucopia/utils/b0.py

@@ -28,11 +28,11 @@
     the `chi_to_fieldmap` function takes *delta* susceptibility values, with
     respect to the air susceptibility. The susceptibility of the air should
     therefore be subtracted from these values before being passed to
-    `mrfield`.
+    `chi_to_fieldmap`.
 
 !!! note
     All values are expressed in ppm (parts per million).
-    They get multiplied by 1e-6 in `mrfield`
+    They get multiplied by 1e-6 in `chi_to_fieldmap`
 
 References
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