Fix documentation of `select` to state that it selects the "last" hypothesis.

tests/tactics.v

@@ -51,3 +51,6 @@ Qed.
 
 Goal ∀ (n : nat), ∃ m : nat, True.
 Proof. intros ?. rename select nat into m. exists m. done. Qed.
+
+Goal ∀ (P : nat → Prop), P 3 → P 4 → P 4.
+Proof. intros. rename select (P _) into HP4. apply HP4. Qed.