Fix casing of TooltipButton

My brain can't deal with two different ways to write "Tooltip", so this
converges the naming to match the rest of the code base. Separate commits will
fix up the file names for case-insensitive file systems.

src/components/views/elements/ToolTipButton.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2017 New Vector Ltd.
+Copyright 2019 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -18,7 +19,7 @@ import React from 'react';
 import sdk from '../../../index';
 
 module.exports = React.createClass({
-    displayName: 'ToolTipButton',
+    displayName: 'TooltipButton',
 
     getInitialState: function() {
         return {
@@ -41,12 +42,12 @@ module.exports = React.createClass({
     render: function() {
         const Tooltip = sdk.getComponent("elements.Tooltip");
         const tip = this.state.hover ? <Tooltip
-            className="mx_ToolTipButton_container"
-            tooltipClassName="mx_ToolTipButton_helpText"
+            className="mx_TooltipButton_container"
+            tooltipClassName="mx_TooltipButton_helpText"
             label={this.props.helpText}
         /> : <div />;
         return (
-            <div className="mx_ToolTipButton" onMouseOver={this.onMouseOver} onMouseOut={this.onMouseOut} >
+            <div className="mx_TooltipButton" onMouseOver={this.onMouseOver} onMouseOut={this.onMouseOut} >
                 ?
                 { tip }
             </div>