main/libvorbis: add secfix comment for CVE-2018-10393

CVE-2018-10393 seems to be a duplicate of CVE-2017-14160

https://gitlab.xiph.org/xiph/vorbis/issues/2334#note_46722

fixes #9527

main/libvorbis/APKBUILD

@@ -24,6 +24,7 @@ builddir="$srcdir/$pkgname-$pkgver"
 #   - CVE-2017-14633
 #   1.3.5-r3:
 #   - CVE-2017-14160
+#   - CVE-2018-10393
 
 prepare() {
 	default_prepare