unbreak TachyonIOS, remove const on bool return value in quick_session.h
unbreak TachyonIOS, remove const on bool return value in quick_session.h

This patch removes a "const" from a bool return value that
was introduced in cl/246926123.
That construct breaks //third_party/objective_c/Tachyon/Tachyon:TachyonStateSyncTests

gfe-relnote: gfe2_reloadable_flag_quic_eliminate_static_stream_map_2 replaces
gfe2_reloadable_flag_quic_eliminate_static_stream_map for rollout purposes.
PiperOrigin-RevId: 246968691
Change-Id: I2fd9855ba27248356513eec82a4af6c4bc3c60fa

google/quiche,google/quiche,google/quiche,google/quiche