Revert "Enable apps grid gap by default"

This reverts commit 4eb610a5.

Reason for revert:  Causing browser crashes when launching the play store on ChromeOS on Octopus machines. b/112321675

Original change's description:
> Enable apps grid gap by default
> 
> Bug: 871448
> Change-Id: I3f8b2c4c9e22065c6615db7d3fab8c8c6b1a7e20
> Reviewed-on: https://chromium-review.googlesource.com/1164245
> Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
> Commit-Queue: Weidong Guo <weidongg@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#581039}

TBR=xiyuan@chromium.org,weidongg@chromium.org

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

Bug: 871448
Change-Id: I4c43f73fead16eb2c8208d9447968775d6d12dba
Reviewed-on: https://chromium-review.googlesource.com/1174780Reviewed-by: Justin TerAvest <teravest@chromium.org>
Reviewed-by: Weidong Guo <weidongg@chromium.org>
Commit-Queue: Justin TerAvest <teravest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583429}

ash/public/cpp/app_list/app_list_features.cc

@@ -23,8 +23,8 @@ const base::Feature kEnableHomeLauncher{"EnableHomeLauncher",
                                         base::FEATURE_ENABLED_BY_DEFAULT};
 const base::Feature kEnableSettingsShortcutSearch{
     "EnableSettingsShortcutSearch", base::FEATURE_DISABLED_BY_DEFAULT};
-const base::Feature kEnableAppsGridGapFeature{"EnableAppsGridGapFeature",
-                                              base::FEATURE_ENABLED_BY_DEFAULT};
+const base::Feature kEnableAppsGridGapFeature{
+    "EnableAppsGridGapFeature", base::FEATURE_DISABLED_BY_DEFAULT};
 const base::Feature kEnableNewStyleLauncher{"EnableNewStyleLauncher",
                                             base::FEATURE_ENABLED_BY_DEFAULT};
 const base::Feature kEnableContinueReading{"EnableContinueReading",