Sync mistral team release liaisons

Mistral team is PTL-less / has distributed PTL role, which is defined
in governance repository [1]. Our check_approval.py script currently
fetches PTL info from governance repository [2] and release liaisons
info from release repository [3]. To make the check approval script
work for all the distributed PTL role owners we need to add them to
release liaisons as well.

[1] 04abe9c3cd/reference/projects.yaml (L816-L824)
[2] reference/projects.yaml
[3] data/release_liaisons.yaml

Change-Id: I5ac426e5112e8f6d3d5b7ec9fe207047e41c33d8

data/release_liaisons.yaml

@@ -80,6 +80,9 @@ mistral:
   - name: 'Renat Akhmerov'
     irc: rakhmerov
     email: renat.akhmerov@gmail.com
+  - name: 'Adriano Petrich'
+    irc: apetrich
+    email: apetrich@redhat.com
 murano:
   - name: 'Rong Zhu'
     irc: zhurong