devel/rubygem-stringio: Update to 3.0.7

Changes:	https://github.com/ruby/stringio/releases
		https://github.com/ruby/stringio/blob/master/NEWS.md

devel/rubygem-stringio/Makefile

 PORTNAME=	stringio
-PORTVERSION=	3.0.6
+PORTVERSION=	3.0.7
 CATEGORIES=	devel rubygems
 MASTER_SITES=	RG
 

devel/rubygem-stringio/distinfo

-TIMESTAMP = 1681843938
-SHA256 (rubygem/stringio-3.0.6.gem) = fbf8bb626f3f835d32922199c42e0e962499fd1d355044445793100469368483
-SIZE (rubygem/stringio-3.0.6.gem) = 16384
+TIMESTAMP = 1685793082
+SHA256 (rubygem/stringio-3.0.7.gem) = b681d64f2b0a7b9a6c1b493795a700bbfa8a083a29a478387ecca4743ed9a714
+SIZE (rubygem/stringio-3.0.7.gem) = 15872