perlreref: fix definition of \R

The order of alternatives matters because Carriage Return (\x0D) is
matched by \v (vertical whitespace), meaning the old pattern was
effectively equivalent to just \v.

Fixes #23002.

Author: mauke

pod/perlreref.pod

@@ -142,7 +142,7 @@ and L<perlunicode> for details.
            like '.' without /s modifier)
    \v      A vertical whitespace
    \V      A non vertical whitespace
-   \R      A generic newline           (?>\v|\x0D\x0A)
+   \R      A generic newline           (?>\x0D\x0A|\v)
 
    \pP     Match P-named (Unicode) property
    \p{...} Match Unicode property with name longer than 1 character