Update gen.sh

plugin/dapp/js/executor/gen.sh

 #!/bin/sh
 
-echo "package executor\n\nvar callcode =  \`" >const.go
+echo "package executor\n\nvar callcode = \`" >const.go
 cat runtime.js >>const.go
 echo '`' >>const.go
 echo 'var jscode = `' >>const.go