Revert "mesa: add missing RGB9_E5 format in _mesa_base_fbo_format"

Revert "mesa: add missing RGB9_E5 format in _mesa_base_fbo_format"

This reverts commit 513c2263cbff45edb105c7b46e58f316e06746ab.

_mesa_base_fbo_format_ is used to validate the internalformat
passed to RenderbufferStorage, which in the OpenGL 4.6 is said:

"An INVALID_ENUM error is generated if internalformat is not one of the
color-renderable, depth-renderable, or stencil-renderable formats defined
in section 9.4."

RGB9_E5 format is not renderable, as stated in the same specification
(Bug 9338).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104794

Cc: Juan A. Suarez Romero <jasuarez@igalia.com>
Cc: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>