PyYAML bug workaround

Change-Id: I7e4ba7e971f160e64837c067002ab9c98741eeb6
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
diff --git a/requirements.in b/requirements.in
index 8a96125..7622148 100644
--- a/requirements.in
+++ b/requirements.in
@@ -20,7 +20,7 @@
 grpclib
 idna
 jinja2
-pyyaml==5.4.1
+pyyaml==5.3.1
 pydantic
 protobuf==3.20.3
 temporalio