Revert "Mentioned https://github.com/ruby/ruby/pull/6086 to NEWS"

This reverts commit 6229c02d6b.

Nothing has been changed in RubyVM.stat on normal Ruby build. It seems
confusing to say that something has been changed there. The flag is
supposed to be enabled only by CRuby developers, and it's not efficient
enough for public consumption.

NEWS.md

@@ -273,10 +273,6 @@ Note: We're only listing outstanding class updates.
 
     * Refinement#refined_class has been added. [[Feature #12737]]
 
-* RubyVM
-
-    * Add debug counters to `RubyVM.stat`. [[GH-6086]]
-
 * RubyVM::AbstractSyntaxTree
 
     * Add `error_tolerant` option for `parse`, `parse_file` and `of`. [[Feature #19013]]
@@ -770,6 +766,5 @@ The following deprecated APIs are removed.
 [Feature #19135]: https://bugs.ruby-lang.org/issues/19135
 [Feature #19138]: https://bugs.ruby-lang.org/issues/19138
 [Feature #19194]: https://bugs.ruby-lang.org/issues/19194
-[GH-6086]:        https://github.com/ruby/ruby/pull/6086
 [GH-6791]:        https://github.com/ruby/ruby/pull/6791
 [GH-6868]:        https://github.com/ruby/ruby/pull/6868