Remove orphaned XUI file

indra/newview/skins/default/xui/en/floater_mfa.xml

@@ -1,49 +0,0 @@
-<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
-<floater
- title="MFA Token Requred"
- legacy_header_height="18"
- can_minimize="false"
- can_close="false"
- height="110"
- layout="topleft"
- name="mfa_challenge"
- help_topic="mfa_challenge"
- width="550">
-    <text
-     type="string"
-     word_wrap="true"
-     length="1"
-     follows="top|left"
-     height="15"
-     layout="topleft"
-     left="10"
-     name="token_prompt_text"
-     top="20">
-        token prompt
-    </text>
-    <line_editor
-     follows="left|top|right"
-     height="19"
-     layout="topleft"
-     bottom_delta="40"
-     name="token_edit"
-     width="100" />
-    <button
-     follows="top|left"
-     height="20"
-     label="Continue"
-     layout="topleft"
-     left="10"
-     name="continue_btn"
-     bottom_delta="30"
-     width="64" />
-    <button
-     follows="top|left"
-     height="20"
-     label="Cancel"
-     layout="topleft"
-     left_pad="5"
-     name="cancel_btn"
-     bottom_delta="0"
-     width="64" />
-</floater>