Fix typo, geekosaur ++

close #1683

Author: tisonkun

doc/Language/regexes.pod6

@@ -284,7 +284,7 @@ L<perlunicode|http://perldoc.perl.org/perlunicode.html> documentation:
 
 For example, C«<:Lu>» matches a single, upper-case letter.
 
-It's negation is this: C«<:!property>». So, C«<:!Lu>» matches a single
+Its negation is this: C«<:!property>». So, C«<:!Lu>» matches a single
 character that isn't an upper-case letter.
 
 Categories can be used together, with an infix operator: