Backport "meson: Fix typo in gobject dependency name" into glib-2-62

Backport of !132 (merged)

This worked fine by accident, but fails when you try to use glib as
a subproject:

glib-networking/meson.build:50:0: ERROR: Inconsistency: Subproject has overriden the dependency with another variable than 'libgobject_dep'