use %r{} instead of // at app/models/repository/subversion.rb

Syntax highlight is broken in gedit 2.28.4 on CentOS 6.

git-svn-id: https://svn.redmine.org/redmine/trunk@11543 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/repository/subversion.rb

@@ -20,7 +20,7 @@ require 'redmine/scm/adapters/subversion_adapter'
 class Repository::Subversion < Repository
   attr_protected :root_url
   validates_presence_of :url
-  validates_format_of :url, :with => /\A(http|https|svn(\+[^\s:\/\\]+)?|file):\/\/.+/i
+  validates_format_of :url, :with => %r{\A(http|https|svn(\+[^\s:\/\\]+)?|file):\/\/.+}i
 
   def self.scm_adapter_class
     Redmine::Scm::Adapters::SubversionAdapter