maven: fix audit

maven:
  * `conflicts_with` (line 31) should be put before `install method` (line 12)

Formula/maven.rb

@@ -9,6 +9,8 @@ class Maven < Formula
 
   depends_on :java
 
+  conflicts_with "mvnvm", :because => "also installs a 'mvn' executable"
+
   def install
     # Remove windows files
     rm_f Dir["bin/*.bat"]
@@ -28,8 +30,6 @@ class Maven < Formula
     end
   end
 
-  conflicts_with "mvnvm", :because => "also installs a 'mvn' executable"
-
   test do
     (testpath/"pom.xml").write <<-EOS.undent
       <?xml version="1.0" encoding="UTF-8"?>