Fix inexistent function reference in poa_components docstring

Author: r0hansaxena

pvlib/irradiance.py

@@ -490,7 +490,7 @@ def poa_components(aoi, dni, poa_sky_diffuse, poa_ground_diffuse):
 
     poa_ground_diffuse : numeric
         Ground-reflected irradiance in the plane of the modules,
-        as calculated by an albedo model (eg. :func:`grounddiffuse`). [Wm⁻²]
+        as calculated by an albedo model (eg. :py:func:`pvlib.irradiance.get_ground_diffuse`). [Wm⁻²]
 
     Returns
     -------