Update LXQt build dependencies.

debian/changelog

@@ -3,6 +3,7 @@ lxqt-session (0.15.0-0ubuntu1) UNRELEASED; urgency=medium
   * New upstream release.
     - Remove reverse-applicable forward-process-output.patch.
     - Update upstream signing key.
+    - Update LXQt build dependencies.
   * Update Standards-version to 4.5.0, no changes needed.
 
  -- Simon Quigley <tsimonq2@ubuntu.com>  Fri, 24 Apr 2020 00:27:35 -0500

debian/control

@@ -8,7 +8,7 @@ Section: x11
 Priority: optional
 Build-Depends: debhelper-compat (= 12),
                libkf5windowsystem-dev,
-               liblxqt0-dev (>= 0.14.1~),
+               liblxqt0-dev (>= 0.15.0),
                libqt5svg5-dev,
                libqt5x11extras5-dev,
                libudev-dev [linux-any],