Removed tracer from ruby repo

Author: hsbt

doc/maintainers.rdoc

@@ -277,10 +277,6 @@ Yukihiro Matsumoto (matz)
   _unmaintained_
   https://github.com/ruby/tmpdir
   https://rubygems.org/gems/tmpdir
-[lib/tracer.rb]
-  Keiju ISHITSUKA (keiju)
-  https://github.com/ruby/tracer
-  https://rubygems.org/gems/tracer
 [lib/tsort.rb]
   Tanaka Akira (akr)
   https://github.com/ruby/tsort

doc/standard_library.rdoc

@@ -72,7 +72,6 @@ Tempfile:: A utility class for managing temporary files
 Time:: Extends the Time class with methods for parsing and conversion
 Timeout:: Auto-terminate potentially long-running operations in Ruby
 tmpdir.rb:: Extends the Dir class to manage the OS temporary file path
-Tracer:: Outputs a source level execution trace of a Ruby program
 TSort:: Topological sorting using Tarjan's algorithm
 un.rb:: Utilities to replace common UNIX commands
 URI:: A Ruby module providing support for Uniform Resource Identifiers