fixed tagging problem in release task

git-svn-id: http://rubygems.rubyforge.org/svn/trunk@692 3d4018f9-ac1a-0410-99e9-8a154d859a19

rubygems/Rakefile

@@ -148,7 +148,7 @@ task :tag => [:prerelease] do
   reltag = "REL_#{ENV['REL'].gsub(/\./, '_')}"
   reltag << "_#{ENV['REUSE']}" if ENV['REUSE']
   announce "Tagging CVS with [#{reltag}]"
-  sh %{cvs tag ${reltag}}
+  sh %{cvs tag #{reltag}}
 end
 
 # --------------------------------------------------------------------