[parser] Drop accumulating non-simple flag

If the outer classifier will end up parsing an arrow parameter list we'd only
be in an inner classifier if the outer was already known to be non-simple.

Change-Id: I9fdfb5539b3a7989869f7190f0919699fe8e5c90
Reviewed-on: https://chromium-review.googlesource.com/c/1276630Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56589}

src/parsing/expression-classifier.h

@@ -191,10 +191,6 @@ class ExpressionClassifierBase {
       // The result will continue to be a valid arrow formal parameters if the
       // inner expression is a valid binding pattern.
       if (productions & ArrowFormalParametersProduction) {
-        // Also whether we've seen any non-simple parameters
-        // if expecting an arrow function parameter.
-        this->is_non_simple_parameter_list_ |=
-            inner->is_non_simple_parameter_list_;
         if (is_valid_arrow_formal_parameters() &&
             !inner->is_valid_binding_pattern()) {
           errors |= ArrowFormalParametersProduction;