vlc-debian-unstable: add QML QtTest dependency

Qt Quick Test was half installed, the C++ classes and .pc file
were present but the QML plugin was missing

vlc-debian-unstable/Dockerfile

@@ -29,7 +29,7 @@ RUN set -x && \
     libswscale-dev wayland-protocols qtbase5-private-dev libarchive-dev \
     libmpg123-dev libnfs-dev curl libltdl-dev libqt5svg5-dev \
     qtdeclarative5-dev qtquickcontrols2-5-dev qml-module-qtquick-controls2 \
-    qml-module-qtquick-layouts qml-module-qtquick-templates2 \
+    qml-module-qtquick-layouts qml-module-qtquick-templates2 qml-module-qttest \
     qml-module-qtgraphicaleffects flex bison libxkbcommon-x11-dev libx11-xcb-dev libplacebo-dev \
     meson doxygen graphviz libsqlite3-dev rapidjson-dev nasm cmake libxcb-damage0-dev \
     clang libc++-dev libc++abi-dev llvm-13 gperf && \