tests/functional: Bump the timeout of the sh4_tuxrun test

When running "make -j$(nproc) check SPEED=thorough", the sh4_tuxrun
test is timing out for me, and using TIMEOUT_MULTIPLIER I can see
that it clearly takes more than 100 seconds to finish. Thus increase
the timeout setting of this test to avoid the problem.

Message-ID: <20241204070757.663119-1-thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/functional/meson.build

@@ -34,6 +34,7 @@ test_timeouts = {
   'ppc64_tuxrun' : 420,
   'riscv64_tuxrun' : 120,
   's390x_ccw_virtio' : 420,
+  'sh4_tuxrun' : 240,
 }
 
 tests_generic_system = [