fix invalid escape sequence '\c' (#1879)

* fix invalid escape sequence '\c'

pvlib/iam.py:843: DeprecationWarning: invalid escape sequence '\c'

Occurence is actually in line 854: `IAM = 1 - (1 - \cos(aoi))^5`

* Add to list of contributors

Author: akeeman

docs/sphinx/source/whatsnew/v0.10.3.rst

@@ -23,4 +23,4 @@ Documentation
 
 Contributors
 ~~~~~~~~~~~~
-
+* Arjan Keeman (:ghuser:`akeeman`)

pvlib/iam.py

@@ -840,7 +840,7 @@ def schlick(aoi):
 
 
 def schlick_diffuse(surface_tilt):
-    """
+    r"""
     Determine the incidence angle modifiers (IAM) for diffuse sky and
     ground-reflected irradiance on a tilted surface using the Schlick
     incident angle model.