updated error for invalid step argument

Author: fpham0701

src/typecheck.rs

@@ -74,7 +74,7 @@ fn check_stmt_types(
                     handler.emit_diagnostic_expr(
                         tr,
                         exprid,
-                        &format!("Incorrect value to step"),
+                        &format!("Step argument must be a positive, non-zero integeral literal."),
                         Level::Error,
                     );
                 }

tests/snapshots/protocols__typecheck__tests__invalid_step_arg.snap

@@ -8,11 +8,11 @@ error: Cannot assign to function argument. Try using assert_eq if you want to ch
 6 │   a := b;
   │   ^^^^^^^ Cannot assign to function argument. Try using assert_eq if you want to check the value of a transaction output.
 
-error: Incorrect value to step
+error: Step argument must be a positive, non-zero integeral literal.
   ┌─ tests/invalid_step_arg.prot:8:8
   │
 8 │   step(0);
-  │        ^ Incorrect value to step
+  │        ^ Step argument must be a positive, non-zero integeral literal.
 
 error: Cannot assign to function argument. Try using assert_eq if you want to check the value of a transaction output.
   ┌─ tests/invalid_step_arg.prot:9:3