Remove outdated reference to icon_installing.png

The Wear recovery UI doesn't draw the installing icon but it was still
trying to open it.  Ever since these images were removed eight months
ago, this has resulted in an error printing to the screen at runtime.
Since the image wasn't really used, the lines to open it can simply be
removed.

Bug: 33203397
Change-Id: Id820f6d75e316c51d19b6095df407ecd61c0410e
diff --git a/wear_ui.cpp b/wear_ui.cpp
index bfa7097..660a078 100644
--- a/wear_ui.cpp
+++ b/wear_ui.cpp
@@ -204,10 +204,11 @@
 void WearRecoveryUI::Init() {
     ScreenRecoveryUI::Init();
 
-    LoadBitmap("icon_installing", &backgroundIcon[INSTALLING_UPDATE]);
-    backgroundIcon[ERASING] = backgroundIcon[INSTALLING_UPDATE];
     LoadBitmap("icon_error", &backgroundIcon[ERROR]);
     backgroundIcon[NO_COMMAND] = backgroundIcon[ERROR];
+
+    // This leaves backgroundIcon[INSTALLING_UPDATE] and backgroundIcon[ERASING]
+    // as NULL which is fine since draw_background_locked() doesn't use them.
 }
 
 void WearRecoveryUI::SetStage(int current, int max)