[DOC] Remove heading with no content [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66561 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

doc/NEWS-2.5.0

@@ -525,8 +525,6 @@ with all sufficient information, see the ChangeLog file or Redmine
 
   * Removed "ubygems.rb" file from stdlib. It's needless since Ruby 1.9.
 
-=== C API updates
-
 === Supported platform changes
 
 * Drop support of NaCl platform

doc/NEWS-2.6.0

@@ -602,8 +602,6 @@ sufficient information, see the ChangeLog file or Redmine
     commands even if the path starts with the pipe character <code>'|'</code>.
     This follows [Feature #14245].
 
-=== C API updates
-
 === Implementation improvements
 
 * Speedup Proc#call because we don't need to care about <code>$SAFE</code>