Revert "add robots.txt to specify doc versions to appear in search engines"

Author: dhalbert

conf.py

@@ -284,7 +284,7 @@
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied
 # directly to the root of the documentation.
-html_extra_path = ["docs/robots.txt"]
+#html_extra_path = []
 
 # If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
 # using the given strftime format.