fix: drop defaults the build has no package for

KNULLI's configgen-defaults.yml picks suyu for the Switch, which its
es_systems.yml does not offer and no package of its tree, its batocera
submodule or its buildroot builds: KNULLI does not ship suyu. A default
es_systems.yml does not offer now counts only when a package of the
build's trees has that name, or when its launcher runs a program from
the BIOS folder (Batocera's lexaloffle). Batocera's lists are unchanged
by the rule. suyu leaves KNULLI's cores, and the XDG_DATA_HOME record
that served it goes.

platforms/knulli.yml

@@ -186,7 +186,6 @@ cores:
 - superbroswar
 - supermodel
 - supermodel-legacy
-- suyu
 - swanstation
 - taradino
 - tgbdual
@@ -4970,7 +4969,6 @@ standalone_cores:
 - stella
 - supermodel
 - supermodel-legacy
-- suyu
 - taradino
 - theforceengine
 - thextech
@@ -6143,14 +6141,6 @@ launchers:
   depends_on_option: not system.name == 'ti99'
   source_ref: "package/system/knulli-configgen/configgen/configgen/generators/libretro/libretroMAMEConfig.py:431-432,\
     \ 435"
-- emulator: suyu
-  build: standalone
-  kind: passes_path
-  names: []
-  search_dir: /userdata/saves/switch
-  passes_to: environment XDG_DATA_HOME
-  fails_when_missing: false
-  source_ref: "package/system/knulli-configgen/configgen/configgen/generators/suyu/suyuGenerator.py:41"
 - emulator: citron
   build: standalone
   kind: passes_path