node-red-pi: fix behavior with old bash version (#1713)

For some reason the following will result
in an endless loop under bash-4.3.42:

while([ -h "${SCRIPT_PATH}" ])

Just remove the round brackets (parentheses) to fix the issue.
They're not needed anyway.

bin/node-red-pi

@@ -31,7 +31,7 @@ done
 # Find the real location of this script
 CURRENT_PATH=`pwd`
 SCRIPT_PATH="${BASH_SOURCE[0]}";
-while([ -h "${SCRIPT_PATH}" ]); do
+while [ -h "${SCRIPT_PATH}" ]; do
     cd "`dirname "${SCRIPT_PATH}"`"
     SCRIPT_PATH="$(readlink "`basename "${SCRIPT_PATH}"`")";
 done