Update lib/net/http/header.rb

Co-authored-by: Jean Boussier <jean.boussier@gmail.com>

Author: baweaver

lib/net/http/header.rb

@@ -491,7 +491,7 @@ def each_capitalized
   alias canonical_each each_capitalized
 
   def capitalize(name)
-    name.to_s.split('-').map {|s| s.capitalize }.join('-')
+    name.to_s.split('-'.freeze).map {|s| s.capitalize }.join('-'.freeze)
   end
   private :capitalize