tests/qtest: Bump the device-introspect-test timeout to 12 minutes

When running the test in slow mode on a very loaded system with the
arm/aarch64 target and with --enable-debug, it can take longer than
10 minutes to finish the introspection test. Bump the timeout to twelve
minutes to make sure that it also finishes in such situations.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20231215070357.10888-13-thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
(cherry picked from commit 50dfa7c)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

tests/qtest/meson.build

@@ -1,6 +1,7 @@
 slow_qtests = {
   'aspeed_smc-test': 360,
   'bios-tables-test' : 540,
+  'device-introspect-test' : 720,
   'migration-test' : 480,
   'npcm7xx_pwm-test': 300,
   'qom-test' : 900,