Merge ~oddbloke/cloud-init/+git/cloud-init:doc into cloud-init:master

[Dan Watkins]

doc: remove intersphinx extension

We don't use it in our doc builds, and if sphinx.pocoo.org is down then
it causes doc build issues.

[Ryan Harper (raharper)]

Nice find.

review: Approve

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:bb3af40dc828aa11fefe88b3905472eb01153503
https://jenkins.ubuntu.com/server/job/cloud-init-ci/1034/
Executed test runs:
    SUCCESS: Checkout
    SUCCESS: Unit & Style Tests
    SUCCESS: Ubuntu LTS: Build
    SUCCESS: Ubuntu LTS: Integration
    IN_PROGRESS: Declarative: Post Actions

Click here to trigger a rebuild:
https://jenkins.ubuntu.com/server/job/cloud-init-ci/1034//rebuild

review: Approve (continuous-integration)

diff --git a/doc/rtd/conf.py b/doc/rtd/conf.py
index 50eb05c..4174477 100644
--- a/doc/rtd/conf.py
+++ b/doc/rtd/conf.py
@@ -27,16 +27,11 @@ project = 'Cloud-Init'
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
 extensions = [
-    'sphinx.ext.intersphinx',
     'sphinx.ext.autodoc',
     'sphinx.ext.autosectionlabel',
     'sphinx.ext.viewcode',
 ]
 
-intersphinx_mapping = {
-    'sphinx': ('http://sphinx.pocoo.org', None)
-}
-
 # The suffix of source filenames.
 source_suffix = '.rst'