[ios]Removes Recent Tabs assets underscores

Followup to https://chromium-review.googlesource.com/c/chromium/src/+/982364

Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I99e1498d85ad296b3c343dafd858fa27d035ef22
Reviewed-on: https://chromium-review.googlesource.com/982391Reviewed-by: edchin <edchin@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546242}

ios/chrome/browser/ui/recent_tabs/resources/BUILD.gn

@@ -8,7 +8,7 @@ imageset("show_history") {
   sources = [
     "show_history.imageset/Contents.json",
     "show_history.imageset/show_history.png",
-    "show_history.imageset/show_history_@2x.png",
-    "show_history.imageset/show_history_@3x.png",
+    "show_history.imageset/show_history@2x.png",
+    "show_history.imageset/show_history@3x.png",
   ]
 }

ios/chrome/browser/ui/table_view/cells/resources/BUILD.gn

@@ -8,8 +8,8 @@ imageset("table_view_cell_chevron") {
   sources = [
     "table_view_cell_chevron.imageset/Contents.json",
     "table_view_cell_chevron.imageset/table_view_cell_chevron.png",
-    "table_view_cell_chevron.imageset/table_view_cell_chevron_@2x.png",
-    "table_view_cell_chevron.imageset/table_view_cell_chevron_@3x.png",
+    "table_view_cell_chevron.imageset/table_view_cell_chevron@2x.png",
+    "table_view_cell_chevron.imageset/table_view_cell_chevron@3x.png",
   ]
 }
 
@@ -17,7 +17,7 @@ imageset("table_view_cell_favicon_background") {
   sources = [
     "table_view_cell_favicon_background.imageset/Contents.json",
     "table_view_cell_favicon_background.imageset/table_view_cell_favicon_background.png",
-    "table_view_cell_favicon_background.imageset/table_view_cell_favicon_background_@2x.png",
-    "table_view_cell_favicon_background.imageset/table_view_cell_favicon_background_@3x.png",
+    "table_view_cell_favicon_background.imageset/table_view_cell_favicon_background@2x.png",
+    "table_view_cell_favicon_background.imageset/table_view_cell_favicon_background@3x.png",
   ]
 }