v13.0 Branch Preparation

Pins version of Flake8
Updates requirements to point to branch

Change-Id: I1db958e754d29e9522d8d4c8167bdb33274951df
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/tox.ini b/tox.ini
index 9f416bc..cd097e1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -54,7 +54,7 @@
 
 #######################################################################################
 [testenv:flake8]
-deps = flake8
+deps = flake8==5.0.4
 commands =
         flake8 osm_pla/ setup.py