gitlab-ci: increase clang-user timeout

The clang-user test exceeds the 1 hour timeout occassionally.

Philippe Mathieu-Daudé has pointed out that the number of tcg tests has
increased since QEMU 7.1. The execution time therefore probably reflects
a legitimate increase in tests rather than a performance regression.

Bump the timeout to prevent CI failures.

Suggested-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20221104113659.427690-1-stefanha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>