Fix build error

Why3 on my local machine is 1.7.2. Bump to 1.8.0 and make sure
that the build works.

Author: VietAnh1010

provers/native/prover_why3.ml

@@ -132,7 +132,7 @@ let attempt_proof task1 =
           let result1 =
             Call_provers.wait_on_call
               (Driver.prove_task
-                ~limit:{Call_provers.empty_limit with limit_time = 0.5}
+                ~limits:{Call_provers.empty_limits with limit_time = 0.5}
                 ~config:why3_config_main
                 ~command:pconf.Whyconf.command
                 pdriver task)