The Right Shift key is recognized as `key.keyboard.unknown` ("Not Bound") with certain input methods

This is an issue where, with certain IMEs, pressing the Right Shift key causes it to be registered as a key.keyboard.unknown (Not Bound) key.
Also, keys assigned to the "Not Bound" function respond to the Right Shift key.

This is an application of MC-310522, and the same behavior can be observed with keys other than the full-screen key.
Since MC-310522 was fixed first, this bug is no longer accessible via keybindings that function across screens—such as those for toggling fullscreen mode or the debug overlay.

Pressing Right Shift on the key assignment screen registers as "Not Bound".
However, it does not register as the Escape key, so it fails to bring up the game menu.
Note that in text boxes, such as the chat area, it functions as the Shift key.

I verified this using the Microsoft Japanese IME.

Verification steps:

1. Unbind the sneak action.

2. You can sneak by pressing Right Shift (e.g., while using the Microsoft Japanese IME).