conf.py: fix warning on html_static_path

A warning is showed when compiling the documentation:

WARNING: html_static_path entry '/home/git/clear-linux-documentation/source/_static' does not exist

After documentation restructure, the _static directory is no more needed.
This commit comment out html_static_path in config.py, and the warning
is not showed.

source/conf.py

@@ -147,7 +147,7 @@
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
+#html_static_path = ['_static']
 
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied