RFR (XXS) 8233658 : Escape + in the expression describing Runtime.Version string

[Ivan Gerasimov]

Hello!

Here's yet another javadoc-only fix.

Format of the Runtime.Version string is described as a list of regular 
expressions [1]:

      $VNUM(-$PRE)?\+$BUILD(-$OPT)?
      $VNUM-$PRE(-$OPT)?
      $VNUM(+-$OPT)?

The character + in the last line should be escaped to be consistent with 
the first line and to avoid confusion with RE quantifiers.

[1] 
https://docs.oracle.com/en/java/javase/13/docs/api/java.base/java/lang/Runtime.Version.html

Would you please help review this trivial one-char fix?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8233658
WEBREV: http://cr.openjdk.java.net/~igerasim/8233658/00/webrev/

-- 
With kind regards,
Ivan Gerasimov