docs.conf: remove _templates from templates_path

This directory doesn't exist so there's no reason to have it listed
there.

docs/source/conf.py

@@ -45,7 +45,7 @@
 ]
 
 # Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
+templates_path = []
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.