Remove workaround include_dir

ios/third_party/material_components_ios/BUILD.gn

Index: ios/third_party/material_components_ios/BUILD.gn
diff --git a/ios/third_party/material_components_ios/BUILD.gn b/ios/third_party/material_components_ios/BUILD.gn
index a86d7f3460b1f144910c98d0b3553391d5fa5f1e..713e75ad69afa4a1b5a6b9c8a50b3b2a046af383 100644
--- a/ios/third_party/material_components_ios/BUILD.gn
+++ b/ios/third_party/material_components_ios/BUILD.gn
@@ -226,9 +226,6 @@ source_set("material_components_ios") {
     "src/components/ButtonBar/src",
     "src/components/NavigationBar/src",
     "src/components/OverlayWindow/src",
-
-    # TODO(crbug.com/684379): remove this include once it is not needed anymore.
-    "src/components/Snackbar/src/private",
     "src/components/private/Application/src",
     "src/components/private/Color/src",
     "src/components/private/Icons/src",