screen_ui: Merge Menu::Start() into its ctor.

Since we instantiate a Menu object each time for a given set of
header/items, we don't have a use case of re-populating an existing Menu
with different data (which is what Menu::Start() does).

Test: mmma -j bootable/recovery
Test: Run recovery_unit_test on marlin.
Test: Build and boot into recovery image on angler. Check the UI.
Change-Id: Iaa2ba9d406ebd74c015e43198c17c5335b38df53
diff --git a/wear_ui.cpp b/wear_ui.cpp
index e4473ba..d21f835 100644
--- a/wear_ui.cpp
+++ b/wear_ui.cpp
@@ -93,8 +93,7 @@
   pthread_mutex_lock(&updateMutex);
   if (text_rows_ > 0 && text_cols_ > 0) {
     menu_ = std::make_unique<Menu>(scrollable_menu_, text_rows_ - kMenuUnusableRows - 1,
-                                   text_cols_ - 1);
-    menu_->Start(headers, items, initial_selection);
+                                   text_cols_ - 1, headers, items, initial_selection);
 
     update_screen_locked();
   }