Fix definition of arb_tez_sizes in test of Tez_repr
In the Test_tez_repr.v
file, change the definition of arb_tez_sizes
so that it does not use an exception anymore, and we can prove its domain.
In the Test_tez_repr.v
file, change the definition of arb_tez_sizes
so that it does not use an exception anymore, and we can prove its domain.