icu: remove libstdc++-devel from depends.

Both compiler packages depend on it already, and its presence makes it
easy to accidentally create build cycles by putting gcc in the
dependency path when it shouldn't be.

srcpkgs/icu/template

@@ -3,7 +3,7 @@
 #       next soname bump.
 pkgname=icu
 version=67.1
-revision=1
+revision=2
 wrksrc=icu
 build_wrksrc=source
 build_style=gnu-configure
@@ -92,7 +92,7 @@ post_install() {
 }
 
 icu-devel_package() {
-	depends="libstdc++-devel icu-libs>=${version}_${revision}"
+	depends="icu-libs>=${version}_${revision}"
 	short_desc+=" - development files"
 	pkg_install() {
 		vmove usr/include