Remove redundant 'Required' annotations from event fields

event-schemas/schema/core-event-schema/event.yaml

@@ -3,11 +3,12 @@ properties:
   content:
     description: The fields in this object will vary depending on the type of event.
       When interacting with the REST API, this is the HTTP body.
-    title: EventContent
     type: object
   type:
     description: The type of event. This SHOULD be namespaced similar to Java package
       naming conventions e.g. 'com.example.subdomain.event.type'
     type: string
+required:
+  - type
 title: Event
 type: object

event-schemas/schema/core-event-schema/room_event.yaml

@@ -4,17 +4,17 @@ description: In addition to the Event fields, Room Events have the following add
   fields.
 properties:
   event_id:
-    description: Required. The globally unique event identifier.
+    description: The globally unique event identifier.
     type: string
   room_id:
-    description: Required. The ID of the room associated with this event.
+    description: The ID of the room associated with this event.
     type: string
   sender:
-    description: Required. Contains the fully-qualified ID of the user who *sent*
+    description: Contains the fully-qualified ID of the user who *sent*
       this event.
     type: string
   origin_server_ts:
-    description: Required. Timestamp in milliseconds on originating homeserver
+    description: Timestamp in milliseconds on originating homeserver
       when this event was sent.
     type: number
   unsigned: