rbr: fix kv_on_cseq:max/2 type spec (regression of r6933)
rbr: fix kv_on_cseq:max/2 type spec (regression of r6933)

note: cannot use is_subtype/2 notation in the two alternatives due to tester limitations
seyyed/scalaris,seyyed/scalaris,digshock/scalaris,seyyed/scalaris,seyyed/scalaris,tectronics/scalaris,tectronics/scalaris,seyyed/scalaris,digshock/scalaris,seyyed/scalaris,seyyed/scalaris,tectronics/scalaris,digshock/scalaris,digshock/scalaris,digshock/scalaris,tectronics/scalaris,digshock/scalaris,tectronics/scalaris,tectronics/scalaris,tectronics/scalaris,digshock/scalaris