Remove obsolete TODO comments about the 'changed' event.

The comments suggested that the 'changed' event fired by
gr-editable-label might be unused, but it is actually used in several
places.

When rendering `<gr-editable-label>`, parent templates `<
gr-editor-view>` and `<gr-change-metadata>` explicitly bind the
`@changed` listener

Release-Notes: skip
Change-Id: I9615093757db01c2db0e320b7a54f1f84def5f45

polygerrit-ui/app/elements/shared/gr-editable-label/gr-editable-label.ts

diff --git a/polygerrit-ui/app/elements/shared/gr-editable-label/gr-editable-label.ts b/polygerrit-ui/app/elements/shared/gr-editable-label/gr-editable-label.ts
index 6c2661f..1261e29 100644
--- a/polygerrit-ui/app/elements/shared/gr-editable-label/gr-editable-label.ts
+++ b/polygerrit-ui/app/elements/shared/gr-editable-label/gr-editable-label.ts
@@ -337,7 +337,6 @@
       this.value = this.inputText || '';
     }
     this.editing = false;
-    // TODO: This event seems to be unused (no listener). Remove?
     fire(this, 'changed', this.value);
   }
 

polygerrit-ui/app/types/events.ts

diff --git a/polygerrit-ui/app/types/events.ts b/polygerrit-ui/app/types/events.ts
index 52a4794..2a2ec16 100644
--- a/polygerrit-ui/app/types/events.ts
+++ b/polygerrit-ui/app/types/events.ts
@@ -110,7 +110,6 @@
 
 export type ChangeEvent = InputEvent;
 
-// TODO: This event seems to be unused (no listener). Remove?
 export type ChangedEvent = CustomEvent<string | undefined>;
 
 export interface ChangeMessageDeletedEventDetail {