Fix: update default.nix to reflect removal of qtct.conf after switch to qtengine

[SamiyelF]

currently, when trying to build on nix, i get this error:

error: Cannot build '/nix/store/lnci4s4b1wdpwgjb5dv73950y6gcnqgs-caelestia-cli-c930bd26045f1f86faa4e19dd082aec5e1754a83.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/6nri1a2r56ch9m2ilnbdwhhpww5k0pg1-caelestia-cli-c930bd26045f1f86faa4e19dd082aec5e1754a83
         /nix/store/l15120svqslga3v8i1pc7xrvphrvyxx2-caelestia-cli-c930bd26045f1f86faa4e19dd082aec5e1754a83-dist
       Last 19 log lines:
       > Sourcing python-remove-tests-dir-hook
       > Sourcing python-catch-conflicts-hook.sh
       > Sourcing python-remove-bin-bytecode-hook.sh
       > Sourcing pypa-build-hook
       > Using pypaBuildPhase
       > Sourcing python-runtime-deps-check-hook
       > Using pythonRuntimeDepsCheckHook
       > Sourcing pypa-install-hook
       > Using pypaInstallPhase
       > Sourcing python-imports-check-hook.sh
       > Using pythonImportsCheckPhase
       > Sourcing python-namespaces-hook
       > Sourcing python-catch-conflicts-hook.sh
       > Running phase: unpackPhase
       > unpacking source archive /nix/store/sfdpfwdazw30s5sld0cnvmy9vqqq22pd-p8ivfsf0mxmf5q14pnrrvsbrfcbps6ac-source
       > source root is p8ivfsf0mxmf5q14pnrrvsbrfcbps6ac-source
       > setting SOURCE_DATE_EPOCH to timestamp 315619200 of file "p8ivfsf0mxmf5q14pnrrvsbrfcbps6ac-source/src/caelestia/utils/wallpaper.py"
       > Running phase: patchPhase
       > substitute(): ERROR: file 'src/caelestia/data/templates/qtct.conf' does not exist
       For full logs, run:
         nix log /nix/store/lnci4s4b1wdpwgjb5dv73950y6gcnqgs-caelestia-cli-c930bd26045f1f86faa4e19dd082aec5e1754a83.drv

note the second to last line: substitute(): ERROR: file 'src/caelestia/data/templates/qtct.conf' does not exist

just updating the line in default.nix that references qtct.conf to reference qtengine.json builds successfully, but thats the extent of my testing. thanks for your work!

[soramanew]

Thanks for the fix!