NEWS.md: remove leading whitespace

NEWS.md

 # NEWS for Ruby 2.8.0 (tentative; to be 3.0.0)
 
-This document is a list of user visible feature changes since the
- **2.7.0** release, except for bug fixes.
+This document is a list of user visible feature changes
+since the **2.7.0** release, except for bug fixes.
 
 Note that each entry is kept so brief that no reason behind or reference
 information is supplied with.  For a full list of changes with all