Update the rst file information

* Update the horizon URL to the new one after doc migration
* Use https instead http
* Adjust title marker length to match the title length

Change-Id: I9c2280793bd8d6496224e36dffd479e1f3732db0
diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 7095b25..49260bc 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -1,18 +1,18 @@
 If you would like to contribute to the development of OpenStack,
 you must follow the steps documented at:
 
-   http://docs.openstack.org/developer/horizon/contributing.html
+    https://docs.openstack.org/horizon/latest/
 
-   or http://docs.openstack.org/infra/manual/developers.html#development-workflow
+    https://docs.openstack.org/infra/manual/developers.html#development-workflow
 
 Once those steps have been completed, changes to OpenStack
 should be submitted for review via the Gerrit tool, following
 the workflow documented at:
 
-   http://docs.openstack.org/infra/manual/developers.html#development-workflow
+    https://docs.openstack.org/infra/manual/developers.html#development-workflow
 
 Pull requests submitted through GitHub will be ignored.
 
 Bugs should be filed on Launchpad, not GitHub:
 
-   https://bugs.launchpad.net/horizon
+    https://bugs.launchpad.net/horizon