Replace SLURP diagram with fancier version

The foundation produced a nicer version of the graphviz generated SLURP
diagram that I made and has asked that we include it in the release
docs. This change adds the image and cleans up the graphviz tooling as
it is no longer required.

Change-Id: Iff4ed3d029975f3a4ca3775e0bd3680cd25aec50

bindep.txt

@@ -9,5 +9,3 @@ git-review [platform:ubuntu]
 libre2-dev [platform:ubuntu]
 # This is for python-pcre which is a dependency of whereto.
 libpcre3-dev [platform:ubuntu]
-# For SLURP graphic rendering
-graphviz [doc]

doc/source/conf.py

@@ -19,7 +19,6 @@ sys.path.insert(0, os.path.join(os.path.abspath('.'), '_exts'))
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
 extensions = [
     'deliverables',
-    'sphinx.ext.graphviz',
     'sphinxcontrib.datatemplates',
     'ics',
     'reviewinbox',

doc/source/index.rst

@@ -98,30 +98,9 @@ supported between these (`SLURP`) releases, in addition to between
 adjacent major releases. For example the upgrade paths starting with
 the 2023.1 Antelope release look like this:
 
-.. graphviz::
+.. image:: _images/slurp.png
-
+   :width: 800
-   digraph openstack_releases {
+   :alt: Slurp Upgrade Path
-     label="OpenStack Upgrade Paths"
-     splines=false;
-     nodesep=1;
-     rankdir="LR";
-     node [shape=box];
-
-     A [label="2023.1\nAntelope"];
-     C [label="2024.1\nCaracal"];
-     B [label="2023.2\nBobcat"];
-     E [label="2025.1\nEpoxy"];
-     D [label="2024.2\nDalmatian"];
-
-     A -> C [xlabel="SLURP"];
-     A -> B;
-     B -> C;
-
-     C -> E [xlabel="SLURP"];
-     C -> D;
-     D -> E;
-
-   }
 
 .. _Skip Level Upgrade Release Process: https://governance.openstack.org/tc/resolutions/20220210-release-cadence-adjustment.html