Bug#1019146: gnome-builder: Update to 43

[Jeremy Bicha]

Source: gnome-builder
Version: 42.1-1+b2
Severity: wishlist
Control: blocks -1 by 1016765
Control: fixed -1 43~alpha1-1

gnome-builder 43 has switched to GTK4 so it needs webkit2gtk's GTK4
libraries (the 5.0 API) for maximum support. More importantly, it
depends on glib 2.73.3 which is stuck in Unstable because of some RC
bugs.

gnome-builder 43 switches to libsoup3 so devhelp (and therefore
anjuta) will need to switch also.

Thank you,
Jeremy Bicha