plugins: Avoid adw deprecation warning
by limiting API to libadwaita 1.5.
This avoids
../plugins/ticket-box/prefs/ticket-box-prefs.c:33:1: warning: ‘adw_preferences_window_get_type’ is deprecated: Use 'AdwPreferencesDialog' instead [-Wdeprecated-declarations]
when building against (unreleased) libadwaita 1.6.
See phosh-mobile-settings#64 (closed)
This avoids --werror
builds don't break during the 0.41 cycle due to that.
Signed-off-by: Guido Günther agx@sigxcpu.org