Remove duplicated definition.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32479 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/matrix.rb

@@ -1764,15 +1764,6 @@ class Vector
   end
   alias map collect
 
-  #
-  # Like Vector#collect2, but returns a Vector instead of an Array.
-  #
-  def map2(v, &block) # :yield: e1, e2
-    return to_enum(:map2, v) unless block_given?
-    els = collect2(v, &block)
-    Vector.elements(els, false)
-  end
-
   #
   # Returns the modulus (Pythagorean distance) of the vector.
   #   Vector[5,8,2].r => 9.643650761