* lib/fileutils.rb: [DOC] Fix typo (s/perserve/preserve/)

[ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43936 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/fileutils.rb

@@ -1649,7 +1649,7 @@ module FileUtils
   #
   #   p FileUtils.have_option?(:cp, :noop)     #=> true
   #   p FileUtils.have_option?(:rm, :force)    #=> true
-  #   p FileUtils.have_option?(:rm, :perserve) #=> false
+  #   p FileUtils.have_option?(:rm, :preserve) #=> false
   #
   def FileUtils.have_option?(mid, opt)
     li = OPT_TABLE[mid.to_s] or raise ArgumentError, "no such method: #{mid}"