tests: Removed 30.eon tests

tests: Removed 30.eon tests

In an effort to cleanup the old tests, and migrate useful tests to be
executed via `test/main.py`, it has been decided that the
`test/long/se/30.eon` tests should be removed.

Jira: https://gem5.atlassian.net/browse/GEM5-109
Change-Id: Ieb32196a5f0ed3b3375ede5aec6f8fb8d162a865
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24386
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>