Since we now target wxWidgets 3.3, all wxCHECK_VERSION(3,1,N) checks
are always true. Remove the guards keeping only the true branches:
- I18N.hpp: Remove version guard around _wxGetTranslation_ctx macro
- ExtraRenderers.hpp, GUI_App.hpp: Simplify SUPPORTS_MARKUP to check
only wxUSE_MARKUP (version check always true)
- ConfigWizard.cpp: Remove manual wxArrayInt comparison fallback
- SendSystemInfoDialog.cpp: Simplify display scaling guard to _WIN32 only
- GUI_Utils.cpp: Remove IsDark() fallback using luma approximation
- wxinit.h: Remove legacy wxEVT_BUTTON and wxEVT_HTML_LINK_CLICKED
compat macros (these event names exist natively in wx 3.3)
