fix main-pane-height.json example

Author: tony

examples/main-pane-height.json

@@ -4,7 +4,7 @@
       "panes": [
         {
           "shell_command": [
-            "vim"
+            "top"
           ], 
           "start_directory": "~"
         }, 
@@ -28,4 +28,4 @@
   ], 
   "session_name": "main pane height", 
   "start_directory": "~"
-}
+}