ART: Remove dequicken map from VerifiedMethod

Remove now unused VerifiedMethod's dequicken map. Follow-up to
c51c7ca7.

Results on a large well-known app in speed compile with -j4:

Before:
 dex2oat took [...] native alloc=84MB [...] swap=208MB [...]
After:
 dex2oat took [...] native alloc=76MB [...] swap=208MB [...]

Bug: 34053922
Test: m clean-oat-host && m test-art-host
Change-Id: Ie95fd297299a0f5fac0c8c702773ee8372f662b6