build: Require libadwaita >= 1.2.beta
split-button dropdown-tooltip was added in libadwaita@75066917
which means nautilus 42.beta.1 will crash if only libadwaita 1.2.alpha is installed
split-button dropdown-tooltip was added in libadwaita@75066917
which means nautilus 42.beta.1 will crash if only libadwaita 1.2.alpha is installed