x11: Skip announcing WM_TAKE_FOCUS in WM_PROTOCOLS

[zzag]

By putting the WM_TAKE_FOCUS atom in the WM_PROTOCOLS property, SDL chooses either the "Locally Active" or "Globally Active" input model depending on the input flag in WM_HINTS.

In order to assist the window manager with making the right decision, for example, skip this window when choosing what window to activate next, it will be better if the WM knows right away that the window accepts or doesn't accept focus (in other words, have either both the input flag set in WM_HINTS + WM_TAKE_FOCUS or none).

Since the WM_TAKE_FOCUS atom is placed in the WM_PROTOCOLS property, the WM wanting to adhere to the spec has no choice but send a client message asking to activate the window and hope for the better.

At quick glance, it appears that the WM_TAKE_FOCUS atom is leftover from SDL_WINDOWEVENT_TAKE_FOCUS, which was dropped a while ago, and is not used anymore. So this change removes the WM_TAKE_FOCUS atom to help window managers such as kwin work better.

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