[iOS] Remove tabs/DEPS

Removes the now-obsolete DEPS file from ios/chrome/browser/tabs.

Bug: 620465
Change-Id: Icc1867e969fab76fdcc6d3577eb6eaddb4c59940
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2117738
Auto-Submit: Mark Cogan <marq@chromium.org>
Reviewed-by: Mohammad Refaat <mrefaat@chromium.org>
Commit-Queue: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753180}

ios/chrome/browser/tabs/DEPS

-specific_include_rules = {
-  # TODO(crbug.com/620465): Remove tab.mm and tab_unittest.mm exceptions.
-  "^tab\.mm$": [
-    "+ios/web/web_state/web_state_impl.h",
-    "+ios/web/web_state/ui/crw_web_controller.h",
-    "+ios/web/navigation/navigation_manager_impl.h",
-  ],
-  "^tab_unittest\.mm$": [
-    "+ios/web/web_state/ui/crw_web_controller.h",
-    "+ios/web/navigation/navigation_manager_impl.h",
-    "+ios/web/navigation/navigation_context_impl.h",
-    "+ios/web/web_state/web_state_impl.h",
-    "+ios/web/test/fakes/crw_fake_back_forward_list.h",
-  ],
-
-  # TODO(crbug.com/620480): tab_model_unittest.mm exceptions.
-  "^tab_model_unittest\.mm$": [
-    "+ios/web/navigation/navigation_manager_impl.h",
-    "+ios/web/web_state/web_state_impl.h",
-  ],
-}