Update LXQt build dependencies.

debian/changelog

@@ -2,6 +2,7 @@ lxqt-powermanagement (0.15.0-0ubuntu1) UNRELEASED; urgency=medium
 
   * New upstream release.
     - Update upstream signing key.
+    - Update LXQt build dependencies.
   * Bump Standards-version to 4.5.0, no changes needed.
 
  -- Simon Quigley <tsimonq2@ubuntu.com>  Thu, 30 Apr 2020 23:24:48 -0500

debian/control

@@ -10,7 +10,7 @@ Build-Depends: debhelper-compat (= 12),
                libkf5idletime-dev,
                libkf5solid-dev,
                libkf5windowsystem-dev,
-               liblxqt0-dev (>= 0.14.1~),
+               liblxqt0-dev (>= 0.15.0),
                libqt5svg5-dev,
                libqt5x11extras5-dev,
                libx11-dev,