Documentation: Fix documentation of infomessage (#9577)

frontend/ui/widget/infomessage.lua

@@ -4,6 +4,7 @@ Widget that displays an informational message.
 It vanishes on key press or after a given timeout.
 
 Example:
+    local InfoMessage = require("ui/widget/infomessage")
     local UIManager = require("ui/uimanager")
     local _ = require("gettext")
     local Screen = require("device").screen
@@ -18,8 +19,7 @@ Example:
         show_icon = false,
         timeout = 5,  -- This widget will vanish in 5 seconds.
     }
-    UIManager:show(sample_input)
-    sample_input:onShowKeyboard()
+    UIManager:show(sample)
 ]]
 
 local Blitbuffer = require("ffi/blitbuffer")