be more ruby-like

Library/Homebrew/cmd/audit.rb

@@ -158,11 +158,12 @@ end
 def audit_formula_version f, text
   # Version as defined in the DSL (or nil)
   version_text = f.class.send('version').to_s
+
   # Version as determined from the URL
   version_url = Pathname.new(f.url).version
 
   if version_url == version_text
-    return [" * version "+version_text+" is redundant with version scanned from url"]
+    return [" * version #{version_text} is redundant with version scanned from url"]
   end
 
   return []