Remove extra '\' left at the end of a line in cache's readme contents

src/_pytest/cacheprovider.py

@@ -112,7 +112,7 @@ class Cache(object):
             """\
         # pytest cache directory #
 
-        This directory contains data from the pytest's cache plugin,\
+        This directory contains data from the pytest's cache plugin,
         which provides the `--lf` and `--ff` options, as well as the `cache` fixture.
 
         **Do not** commit this to version control.