Drop incubating theme from docs

OpenStack has dropped the incubation notion, so labeling this as an
incubated project in the docs is confusing.

Change-Id: I1893fa76affb5e712abef6765e373077b2fc6832

doc/source/conf.py

@@ -130,7 +130,7 @@ modindex_common_prefix = ['zaqarclient.']
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-html_theme_options = {'incubating': True}
+html_theme_options = {}
 
 # Add any paths that contain custom themes here, relative to this directory.
 #html_theme_path = []