doc: remove trailing whitespace

PR-URL: #24642
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

README.md

@@ -62,7 +62,7 @@ The open source license grants you the freedom to use Node.js. It does not
 guarantee commitments of other people's time. Please be respectful and manage
 your expectations.
 
-## Release Types 
+## Release Types
 
 * **Current**: Under active development. Code for the Current release is in the
   branch for its major version number (for example,