change hint in edit subject dialog

src/main/java/eu/siacs/conversations/ui/ConferenceDetailsActivity.java

@@ -280,7 +280,7 @@ public class ConferenceDetailsActivity extends XmppActivity implements OnConvers
 			case R.id.action_edit_subject:
 				if (mConversation != null) {
 					quickEdit(mConversation.getMucOptions().getSubject(),
-							R.string.action_edit_subject,
+							R.string.edit_subject_hint,
 							this.onSubjectEdited);
 				}
 				break;

src/main/res/values/strings.xml

@@ -250,6 +250,7 @@
 	<string name="bookmark_already_exists">This bookmark already exists</string>
 	<string name="you">You</string>
 	<string name="action_edit_subject">Edit conference subject</string>
+	<string name="edit_subject_hint">The subject of this conference</string>
 	<string name="joining_conference">Joining conference…</string>
 	<string name="leave">Leave</string>
 	<string name="contact_added_you">Contact added you to contact list</string>