fix path

Author: knakayama

scripts/tmux_open_error_message.sh

@@ -2,7 +2,7 @@
 
 CURRENT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 
-source "$CURRENT_DIR/scripts/helpers.sh"
+source "$CURRENT_DIR/helpers.sh"
 
 MISSING_PROGRAM="$1"