DEBUGGER__::Context::debug_print_help: Typo fix of help message.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@3037 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/debug.rb

@@ -529,7 +529,7 @@ class Context
     stdout.print <<EOHELP
 Debugger help v.-0.002b
 Commands
-  b[reak] [file|method:]<line|method>
+  b[reak] [file:]<line|method>
                              set breakpoint to some position
   wat[ch] <expression>       set watchpoint to some expression
   cat[ch] <an Exception>     set catchpoint to an exception