Fix zuul.projects type in docs

There was a second location where the old "list" type was used in the
docs that was missed in the change to dict of dicts. Fix this minor
documentation detail to say dictionary instead of list.

Change-Id: I4c9f90f201040e3044e818b839fc715e906f049d
diff --git a/doc/source/user/jobs.rst b/doc/source/user/jobs.rst
index ae720d8..278c4f4 100644
--- a/doc/source/user/jobs.rst
+++ b/doc/source/user/jobs.rst
@@ -222,7 +222,7 @@
    .. var:: projects
       :type: dict
 
-      A list of all projects prepared by Zuul for the item.  It
+      A dictionary of all projects prepared by Zuul for the item.  It
       includes, at least, the item's own project.  It also includes
       the projects of any items this item depends on, as well as the
       projects that appear in :attr:`job.required-projects`.