small fix

Author: CoderDake

tool/release_helper.sh

@@ -8,7 +8,7 @@ if [ -z "$TYPE" ] ; then
     exit 1
 fi
 
-if [ -z "$DEVTOOLS_REMOTE" } ] ; then
+if [ -z "$DEVTOOLS_REMOTE" ] ; then
     echo "Couldn't find a remote that points to flutter/devtools.git"
     exit 1
 fi