Revert to local icon image

Shared version of lock icon looks weird in context

src/images/icons/lock.svg

+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg width="48px" height="56px" viewBox="0 0 48 56" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+    <g stroke="none" stroke-width="1" fill="none" fill-rule="evenodd">
+        <g fill="currentColor">
+            <rect x="0" y="24" width="48" height="32"></rect>
+            <path d="M24,0 C24,0 8,0 8,16 L8,32 L16,32 L16,16.0000004 C16,8 24,8 24,8 C24,8 32,8 32,16 L32,32 L40,32 L40,16 C40,0 24,0 24,0 Z"></path>
+        </g>
+    </g>
+</svg>
\ No newline at end of file

src/sidebar/icons.js

@@ -29,7 +29,6 @@ import {
   listOrdered,
   listUnordered,
   logo,
-  lock,
   plus,
   profile,
   refresh,
@@ -43,6 +42,7 @@ import {
 
 // The following icons differ here from the shared-package versions
 import annotateIcon from '../images/icons/annotate.svg';
+import lockIcon from '../images/icons/lock.svg';
 import replyIcon from '../images/icons/reply.svg';
 import sortIcon from '../images/icons/sort.svg';
 
@@ -88,7 +88,7 @@ export default {
   image,
   leave,
   link,
-  lock,
+  lock: lockIcon,
   logo,
   pointer: pointerIcon,
   profile,