[iOS] Remove tab grid showcase

This showcase is crashing, as it is not tested, the investigation to
understand when it is been introduce is impossible. No alert been raised
about the fact that tab grid showcase did not work, so it looks like
nobody use it. This CL removes tab grid showcase.

Change-Id: I2c1a40f80993db9bf0f5bcf04ee221711a3dcde8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4952175
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Aliona Dangla <alionadangla@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1211484}

ios/showcase/BUILD.gn

@@ -44,7 +44,6 @@ group("features") {
     "//ios/showcase/omnibox_popup",
     "//ios/showcase/recent_tabs",
     "//ios/showcase/settings",
-    "//ios/showcase/tab_grid",
     "//ios/showcase/text_badge_view",
     "//ios/showcase/uikit_table_view_cell",
     "//ios/showcase/user_policy_prompt",

ios/showcase/core/showcase_model.mm

@@ -98,32 +98,6 @@ @implementation ShowcaseModel
       showcase::kClassForInstantiationKey : @"SCBubbleCoordinator",
       showcase::kUseCaseKey : @"Bubble",
     },
-    @{
-      showcase::kClassForDisplayKey : @"GridViewController",
-      showcase::kClassForInstantiationKey : @"SCGridCoordinator",
-      showcase::kUseCaseKey : @"Grid UI",
-    },
-    @{
-      showcase::kClassForDisplayKey : @"GridCell",
-      showcase::kClassForInstantiationKey : @"SCGridCellViewController",
-      showcase::kUseCaseKey : @"Grid cells",
-    },
-    @{
-      showcase::kClassForDisplayKey : @"TabGridViewController",
-      showcase::kClassForInstantiationKey : @"SCTabGridCoordinator",
-      showcase::kUseCaseKey : @"Full tab grid UI",
-    },
-    @{
-      showcase::
-      kClassForDisplayKey : @"TabGridTopToolbar, TabGridBottomToolbar",
-      showcase::kClassForInstantiationKey : @"SCToolbarsViewController",
-      showcase::kUseCaseKey : @"Toolbars for tab grid",
-    },
-    @{
-      showcase::kClassForDisplayKey : @"TopAlignedImageView",
-      showcase::kClassForInstantiationKey : @"SCImageViewController",
-      showcase::kUseCaseKey : @"ImageView with top aligned aspect fill",
-    },
     @{
       showcase::kClassForDisplayKey : @"RecentTabsTableViewController",
       showcase::kClassForInstantiationKey : @"SCDarkThemeRecentTabsCoordinator",