Add default rule to suppress notices.

synapse/push/baserules.py

@@ -104,6 +104,19 @@ def make_base_override_rules():
 
 def make_base_underride_rules():
     return [
+        {
+            'rule_id': 'global/underride/.m.rule.suppress_notices',
+            'conditions': [
+                {
+                    'kind': 'event_match',
+                    'key': 'content.msgtype',
+                    'pattern': 'm.notice',
+                }
+            ],
+            'actions': [
+                'dont-notify',
+            ]
+        },
         {
             'rule_id': 'global/underride/.m.rule.fallback',
             'conditions': [