recovery: Clarify help text

Currently this help text is not rendered, but that will change in a
future commit.

Change-Id: Ic2f566b84c4f49610fe0dab5929abe19abef9275
diff --git a/recovery_ui/screen_ui.cpp b/recovery_ui/screen_ui.cpp
index ed6ae19..952dd7e 100644
--- a/recovery_ui/screen_ui.cpp
+++ b/recovery_ui/screen_ui.cpp
@@ -777,7 +777,8 @@
 std::vector<std::string> ScreenRecoveryUI::GetMenuHelpMessage() const {
   // clang-format off
   static std::vector<std::string> REGULAR_HELP{
-    "Use volume up/down and power.",
+    "Use the volume up/down keys to navigate.",
+    "Use the power key to select.",
   };
   static std::vector<std::string> LONG_PRESS_HELP{
     "Any button cycles highlight.",