Remove QuicMakeUnique, Http2MakeUnique, SpdyMakeUnique from platform/api/.
NOTE to QUICHE embedders:
*MakeUniqueImpl should be removed from {quic,http2,spdy}/platform/impl/.
gfe-relnote: n/a, no functional change.
PiperOrigin-RevId: 277329927
Change-Id: Ied8e6ccd5d9d900cf1833e1030d1bf259b201c47