Bump LXQt build dependencies.

debian/changelog

@@ -2,6 +2,7 @@ lxqt-config (0.15.0-0ubuntu1) UNRELEASED; urgency=medium
 
   * New upstream release.
     - Update upstream signing key.
+    - Bump LXQt build dependencies.
     - Add build dependency on libxcb-randr0-dev (Closes: #952266).
   * Bump Standards-version to 4.5.0, no changes needed.
   * debhelper -> debhelper-compat.

debian/control

@@ -7,7 +7,7 @@ Priority: optional
 Build-Depends: debhelper-compat (= 12),
                libkf5screen-dev,
                libkf5windowsystem-dev,
-               liblxqt0-dev (>= 0.14.0),
+               liblxqt0-dev (>= 0.15.0),
                libqt5svg5-dev,
                libqt5x11extras5-dev,
                libx11-dev,