Remove severity level for SBE attention event

The severity level will be specified by the creator.

Signed-off-by: Ben Tyner <ben.tyner@ibm.com>
Change-Id: I4546513f6c2357d1fcd3ca2b6441815ede573c90
diff --git a/extensions/openpower-pels/registry/message_registry.json b/extensions/openpower-pels/registry/message_registry.json
index 317dd3e..904d255 100644
--- a/extensions/openpower-pels/registry/message_registry.json
+++ b/extensions/openpower-pels/registry/message_registry.json
@@ -1373,7 +1373,6 @@
         {
             "Name": "org.open_power.Attn.Error.Vital",
             "Subsystem": "processor_chip",
-            "Severity": "critical",
 
             "SRC": {
                 "ReasonCode": "0xD16D",