Remove utils/tests involving SecurityManager (#3440)

Remove tests that were relying on use of the Java 17-deprecated
SecurityManager.  These does decrease test coverage of "no file writing"
and "exit code checking" behaviors.  However, there doesn't appear to be a
viable workaround for this for testing inside the JVM, i.e., using
Scalatest.

See: https://openjdk.org/jeps/411



Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>