Fix rbac rpk syntax (#895)

Author: Deflaimun

modules/manage/pages/security/authorization/rbac.adoc

@@ -44,8 +44,8 @@ Consider a scenario where your software engineers use a set of private topics to
 
 [,bash]
 ----
-rpk security role create SoftwareEng \&\&
-rpk security acl create --operation read --operation write --topic private-* --allow-role SoftwareEng \&\&
+rpk security role create SoftwareEng &&
+rpk security acl create --operation read --operation write --topic private-* --allow-role SoftwareEng &&
 rpk security role assign SoftwareEng --principal User:john,User:jane
 ----