Remove .qmake.conf from this repository

This file was necessary for the qmake build and the CI.  The qmake
build is history, and the CI does now read .cmake.conf (see
QTQAINFRA-4392).

In addition to being superfluous, the existence of .qmake.conf
triggers QTBUG-76140 when building Qt examples with qmake.  Removing
the file alleviates the symptoms of this bug.

Fixes: QTBUG-92271
Change-Id: I6bb8a0ba5ad2d145bd639e265d29b0a0bb5806dc
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>

.qmake.conf

-load(qt_build_config)
-
-MODULE_VERSION = 6.2.0