Fix typo for LoadError constant

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49017 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/rbinstall.rb

@@ -711,7 +711,7 @@ end
 install?(:ext, :comm, :gem) do
   begin
     require "zlib"
-  rescue LoadErroe
+  rescue LoadError
   end
   if defined?(Zlib)
     require 'pathname'