Use simple quote instead of double in sanity check

Author: acogoluegnes

Diff for: src/main/scripts/sanity-check.groovy

@@ -1,6 +1,6 @@
 @GrabResolver(name = 'rabbitmq-bintray', root = 'http://dl.bintray.com/rabbitmq/maven')
 @GrabResolver(name = 'rabbitmq-packagecloud-milestones', root = 'https://packagecloud.io/rabbitmq/maven-milestones/maven2')
-@Grab(group = 'com.rabbitmq', module = 'amqp-client', version = "${version}")
+@Grab(group = 'com.rabbitmq', module = 'amqp-client', version = '${version}')
 @Grab(group = 'org.slf4j', module = 'slf4j-simple', version = '1.7.25')
 import com.rabbitmq.client.AMQP
 import com.rabbitmq.client.Channel