wgl/glx: Fix attribute list for SDL_GL_FLOATBUFFERS
This commit fixes the attribute list in the WGL and GLX code when requesting a floating point pixel format. The name of the attribute was missing in the list.
Fixes libsdl-org#10189
(cherry picked from commit 938971291761ba8ea1e776347cb1cf3dafe6d549)
(cherry picked from commit 58e179c8b50feff2a321003886f218a7b006c4d0)