webkitgtk: Bump up version to 2.34.0

[psaavedra]

First stable release in the 2.34 series.

• Add support for HTTP/2 when building with libsoup3.
• Add support for CSS Scroll Snap.
• Add support for date and datetime-local input elements.
• Add support for display capture.
• Add support for ICC color management.
• Add support color-schemes CSS property.
• Add support for link preconnect when building with libsoup3.
• Add support for client side certificates when building with libsoup3.
• Add multi-track support to MSE media backend.
• Add new API to handle web process unresponsiveness.
• Add API to disable CORS on a web view for particular domains.
• Add new API to access/modify capture devices states.
• Add new API to configure the memory pressure handler.
• For more details about all the changes included in WebKitGTK 2.34 see the NEWS file that is included in the tarball.

Release note:

• https://webkitgtk.org/2021/09/22/webkitgtk2.34.0-released.html