EventIndex: Use a warning when redactions don't have an event id.

Co-authored-by: Travis Ralston <travpc@gmail.com>

src/indexing/EventIndex.js

@@ -512,8 +512,7 @@ export default class EventIndex extends EventEmitter {
                     if (eventId) {
                         await indexManager.deleteEvent(eventId);
                     } else {
-                        console.log("EventIndex: Redaction event doesn't contain a",
-                                    "valid associated event id", ev);
+                        console.warn("EventIndex: Redaction event doesn't contain a valid associated event id", ev);
                     }
                 }