flatpak: add libde265

x265 module was there two times but libde265 was missing.

PS:

I tried to build locally using flatpak-builder but module gmic-qt failed. I think it is unrelated to my commit:

-- Build files have been written to: /run/build/gmic-qt/_flatpak_build
[1/86] Automatic MOC for target Editor_GmicQt_Plugin
[2/86] Generating ui_filtersview.h
[3/86] Generating ui_dialogsettings.h
[4/86] Generating ui_headlessprogressdialog.h
[5/86] Generating ui_inoutpanel.h
[6/86] Automatic RCC for gmic_qt.qrc
[7/86] Automatic RCC for translations.qrc
[8/86] Generating ui_languageselectionwidget.h
[9/86] Generating ui_mainwindow.h
[10/86] Generating ui_multilinetextparameterwidget.h
[11/86] Generating ui_progressinfowidget.h
[12/86] Generating ui_progressinfowindow.h
[13/86] Generating ui_SearchFieldWidget.h
[14/86] Generating ui_zoomlevelselector.h
[15/86] Building CXX object CMakeFiles/Editor_GmicQt_Plugin.dir/Editor_GmicQt_Plugin_autogen/mocs_compilation.cpp.o
FAILED: CMakeFiles/Editor_GmicQt_Plugin.dir/Editor_GmicQt_Plugin_autogen/mocs_compilation.cpp.o
/run/ccache/bin/c++ -DEditor_GmicQt_Plugin_EXPORTS -DGMIC_HOST=digikam -DQT_CORE_LIB -DQT_GUI_LIB -DQT_NETWORK_LIB -DQT_NO_DEBUG -DQT_NO_DEBUG_OUTPUT -DQT_WIDGETS_LIB -D_IS_LINUX_ -D_IS_UNIX_ -Dcimg_appname=\"gmic\" -Dcimg_display=1 -Dcimg_use_abort -Dcimg_use_cpp11=1 -Dcimg_use_curl -Dcimg_use_fftw3 -Dcimg_use_openmp -Dcimg_use_png -Dcimg_use_vt100 -Dcimg_use_zlib -Dgmic_build -Dgmic_gui -Dgmic_is_parallel -I. -I../ -IEditor_GmicQt_Plugin_autogen/include -I../src -I.././gmic/src -I/app/include/digikam -isystem /usr/include/QtCore -isystem /usr/lib/mkspecs/linux-g++ -isystem /usr/include/QtWidgets -isystem /usr/include/QtGui -isystem /usr/include/QtNetwork -O2 -g -pipe -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -fopenmp -flto -fexceptions  -DNDEBUG -Ofast -fPIC   -fopenmp -fPIC -std=gnu++11 -MD -MT CMakeFiles/Editor_GmicQt_Plugin.dir/Editor_GmicQt_Plugin_autogen/mocs_compilation.cpp.o -MF CMakeFiles/Editor_GmicQt_Plugin.dir/Editor_GmicQt_Plugin_autogen/mocs_compilation.cpp.o.d -o CMakeFiles/Editor_GmicQt_Plugin.dir/Editor_GmicQt_Plugin_autogen/mocs_compilation.cpp.o -c Editor_GmicQt_Plugin_autogen/mocs_compilation.cpp
In file included from /app/include/digikam/dplugineditor.h:24,
                 from Editor_GmicQt_Plugin_autogen/2UTX2OFSXO/../../../src/Host/digiKam/gmicqttoolplugin.h:30,
                 from Editor_GmicQt_Plugin_autogen/2UTX2OFSXO/moc_gmicqttoolplugin.cpp:10,
                 from Editor_GmicQt_Plugin_autogen/mocs_compilation.cpp:29:
/app/include/digikam/dinfointerface.h:39:10: fatal error: dmetadata.h: No such file or directory
   39 | #include "dmetadata.h"
      |          ^~~~~~~~~~~~~
compilation terminated.
[16/86] Building CXX object CMakeFiles/Editor_GmicQt_Plugin.dir/src/Common.cpp.o
[17/86] Building CXX object CMakeFiles/Editor_GmicQt_Plugin.dir/src/OverrideCursor.cpp.o
[18/86] Building CXX object CMakeFiles/Editor_GmicQt_Plugin.dir/src/ClickableLabel.cpp.o
ninja: build stopped: subcommand failed.