package/webkitgtk: security bump to 2.30.6

package/webkitgtk: security bump to 2.30.6

This is a minor release which provides fixes for CVE-2020-27918,
CVE-2020-29623, CVE-2021-1765, CVE-2021-1789, CVE-2021-1799,
CVE-2021-1801, and CVE-2021-1870.

Full release notes can be found at:

  https://webkitgtk.org/2021/03/18/webkitgtk2.30.6-released.html

An accompanying security advisory has been published at:

  https://webkitgtk.org/security/WSA-2021-0002.html

Signed-off-by: Adrian Perez de Castro <aperez@igalia.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>