Revert "[ios] Change EmbedderBlockRestoreUrl default official value."

This reverts commit 7798da0c.

Reason for revert: Enable by default again for M80.

Original change's description:
> [ios] Change EmbedderBlockRestoreUrl default official value.
> 
> Change-Id: Ib1049641e3035846e6e26ca545206dc28e576ece
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1929266
> Commit-Queue: Justin Cohen <justincohen@chromium.org>
> Reviewed-by: Rohit Rao <rohitrao@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#718157}

TBR=rohitrao@chromium.org,justincohen@chromium.org

Change-Id: I10827d3b4cfa295b4f9d40ffb54b193b2dbf2273
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1931201Reviewed-by: Justin Cohen <justincohen@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718286}

ios/chrome/browser/ui/ui_feature_flags.cc

@@ -29,7 +29,7 @@ const base::Feature kLanguageSettings{"LanguageSettings",
                                       base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kEmbedderBlockRestoreUrl{"EmbedderBlockRestoreUrl",
-                                             base::FEATURE_DISABLED_BY_DEFAULT};
+                                             base::FEATURE_ENABLED_BY_DEFAULT};
 
 const base::Feature kDisableAnimationOnLowBattery{
     "DisableAnimationOnLowBattery", base::FEATURE_DISABLED_BY_DEFAULT};