gdkkeys-win32: Ignore CTRL bit for key translation
Some keymaps on Windows contain bogus mappings for Ctrl+key for certain keys, e.g. Ctrl+Backspace = Delete, or Ctrl+[ = 0x1B. These are never used on Windows, so we should ignore them.
Forward-port of !4423 (merged) to GTK4
Fixes #4667 (closed)