minor cleanup

Author: jpederzolli

src/main/java/com/cloudbees/jenkins/plugins/docker_build_env/Docker.java

@@ -338,7 +338,7 @@ public EnvVars getEnv(String container, Launcher launcher) throws IOException, I
     }
 
 
-    public void executeIn(String container, String userId, Launcher.ProcStarter starter, EnvVars environment, Set sensitiveBuildVariables) throws IOException, InterruptedException {
+    public void executeIn(String container, String userId, Launcher.ProcStarter starter, EnvVars environment, Set<String> sensitiveBuildVariables) throws IOException, InterruptedException {
         List<String> prefix = dockerCommandArgs();
         prefix.add("exec");
         prefix.add("--tty");