Don't test Platform 2011.4.0.0
Don't test Platform 2011.4.0.0

It fails due to a constraint on a newer deepseq in Cabal-1.18 than what
is available.

We could technically install another Cabal version here, but I won't
deal with it for now.

Signed-off-by: Austin Seipp <48c905ac3851f382b914247d97dd93273d5ff555@pobox.com>

thoughtpolice/hs-ed25519,thoughtpolice/hs-ed25519