Use SIGTERM to terminate test-introspection

The test-introspection binary has a custom SIGINT handler that tells the user to press Ctrl-C again to quit. Although sending two SIGINTs with a delay in between "works", it's still a bit racy, so just switch to SIGTERM instead.

https://phabricator.apertis.org/T8377

Signed-off-by: Ryan Gonzalez ryan.gonzalez@collabora.com