gtk.cfg: Remove transfer none function g_application_get_default

[Tamaranch]

See https://docs.gtk.org/gio/type_func.Application.get_default.html

[chrchr-github]

Thanks for your contribution, please add a test to test/cfg/gtk.c.

[Tamaranch]

Thanks for your contribution, please add a test to test/cfg/gtk.c.

Done. Note that I need to add --check-level=exhaustive and remove an inline suppression to run the tests with exitcode=0:

Checking test/cfg/gtk.c ...
test/cfg/gtk.c:0:0: information: Limiting analysis of branches. Use --check-level=exhaustive to analyze all branches. [normalCheckLevelMaxBranches]

^
test/cfg/gtk.c:83:0: information: Unmatched suppression: valueFlowBailout [unmatchedSuppression]
        printf("%s", str);
^
nofile:0:0: information: Active checkers: 118/186 (use --checkers-report=<filename> to see details) [checkersReport]