NEWS: move the section to note ERB performance

I heard that notable performance improvements should be written to
"Implementation Improvements". So I put the sentence here.

Also, the sentence itself is fixed to be the same as Ruby 2.5 release
note draft's one.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61451 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

NEWS

@@ -316,8 +316,6 @@ with all sufficient information, see the ChangeLog file or Redmine
 
 * ERB
 
-  * Rendering of ERB's compiled code becomes 2x faster.
-
   * Add ERB#result_with_hash to render a template with local variables passed
     with a Hash object. [Feature #8631]
 
@@ -535,6 +533,8 @@ with all sufficient information, see the ChangeLog file or Redmine
 * Dynamic instrumentation for TracePoint hooks instead of using "trace"
   instruction to avoid overhead [Feature #14104]
 
+* ERB now generates code from a template which runs 2 times faster than Ruby 2.4
+
 === Miscellaneous changes
 
 * Print backtrace and error message in reverse order if STDERR is unchanged and a tty.