docs: Actually configure reno to use the main branch

I used the wrong setting [1]

[1] https://docs.openstack.org/reno/latest/user/usage.html#configuring-reno

Signed-off-by: Stephen Finucane <stephen@that.guru>
(cherry picked from commit b39dabf)
(cherry picked from commit b89ba00)

Author: stephenfin

releasenotes/config.yaml

@@ -1,5 +1,5 @@
 ---
-branch: main
+default_branch: main
 release_tag_re: 'v\d\.\d\.\d(rc\d+)?'
 pre_release_tag_re: '(?P<pre_release>-rc(?:\d)*)$'
 sections:

tools/post-receive.hook

@@ -11,7 +11,7 @@ set -eu
 PW_DIR=/opt/patchwork/patchwork
 
 #TODO: the state map should really live in the repo's git-config
-STATE_MAP="refs/heads/master:Accepted"
+STATE_MAP="refs/heads/main:Accepted"
 
 # ignore all commits already present in these refs
 # e.g.,