mem-ruby: MESI_Two_Level missing function compilation fix

mem-ruby: MESI_Two_Level missing function compilation fix

The recent commit dd6cd33 removed the Ruby Sequencer function
invalidateSC in favour of doing this implicitely via
evictionCallback. The protocol MESI_Two_Level still contains one
explicit call to this function, however, this is now superflous
as forward_eviction_to_cpu is called in the same transition. This
patch removes the remaining calls to invalidateSC.

JIRA: https://gem5.atlassian.net/browse/GEM5-499

Change-Id: If51d8bebf6aa39d20789639aab0d262d5173ca59
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28747
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Ayaz Akram <yazakram@ucdavis.edu>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>