Drop enabling maybe_expr in the runtime - it's not needed anymore

Author: erszcz

rebar.config

@@ -4,10 +4,7 @@
           {deps,
            [
             {proper, {git, "https://github.com/proper-testing/proper.git", {branch, "master"}}}
-           ]},
-          %% see the maybe expression fail;
-          %% the VM also needs to be configured to load the module
-          {erl_opts, [{feature,maybe_expr,enable}]}
+           ]}
          ]}
  ]}.