docs(api): make event argument in fireEvent optional (#11371)

Author: ffMathy

apidoc/Titanium/Proxy.yml

@@ -58,6 +58,7 @@ methods:
 summary: Name of the event.
 type: String
  - name: event
+optional: true
 summary: A dictionary of keys and values to add to the <Titanium.Event> object
 sent to the listeners.
 type: Dictionary
@@ -105,4 +106,4 @@ properties:
  to the appropriate containing Window or TabGroup.
 type: [Titanium.UI.Window, Titanium.UI.TabGroup]
 platforms: [android]
-since: "3.6.0"
+since: "3.6.0"