Revert "Temporarily disable frozen/sealed elements kinds"

This reverts commit 77476cb2.

Reason for revert: This is no longer necessary. Let's continue getting test coverage for new elements kinds.

Original change's description:
> Temporarily disable frozen/sealed elements kinds
> 
> ... to prepare for merging this back to stable chanel.
> 
> Bug: chromium:972921
> Change-Id: I04ced1c81b5f8730014ecee8935799fccc377a49
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1667006
> Commit-Queue: Igor Sheludko <ishell@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#62283}

TBR=ishell@chromium.org,verwaest@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:972921
Change-Id: I3686bd0f45d354f4826711671a10f1ef7b915e20
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1675953Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62351}

src/flags/flag-definitions.h

@@ -357,7 +357,7 @@ DEFINE_BOOL(enable_one_shot_optimization, true,
             "only be executed once")
 
 // Flag for sealed, frozen elements kind instead of dictionary elements kind
-DEFINE_BOOL_READONLY(enable_sealed_frozen_elements_kind, false,
+DEFINE_BOOL_READONLY(enable_sealed_frozen_elements_kind, true,
                      "Enable sealed, frozen elements kind")
 
 // Flags for data representation optimizations