Fix a class of a returned value

* ext/objspace/object_tracing.c (allocation_sourceline): Fix
  a class of a returned value. allocation_sourceline returns
  an integer.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59587 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/objspace/object_tracing.c

@@ -356,7 +356,7 @@ allocation_sourcefile(VALUE self, VALUE obj)
 }
 
 /*
- * call-seq: allocation_sourceline(object) -> string
+ * call-seq: allocation_sourceline(object) -> integer
  *
  * Returns the original line from source for from the given +object+.
  *