test for one pair
Examples
d = build_deck()
hand_1 = c(d[1], d[14], d[2:4] )
hand_1
#> [1] "2 ♡" "2 ♢" "3 ♡" "4 ♡" "5 ♡"
one_pair(hand_1[1])
#> [1] FALSE
hand_2 = c(d[1], d[6], d[2:4] )
hand_2
#> [1] "2 ♡" "7 ♡" "3 ♡" "4 ♡" "5 ♡"
one_pair(hand_2[2])
#> [1] FALSE