[iOS] Remove deps target used for compatibility

This target was used for downstream compatibility.
Land this CL after downstream CL lands.

Bug: none
Change-Id: I204c794b592d9746e18d4a2083bb46a44cd7199b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1913408Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714919}

ios/chrome/test/base/BUILD.gn

@@ -2,15 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("base") {
-  configs += [ "//build/config/compiler:enable_arc" ]
-  testonly = true
-  sources = []
-  public_deps = [
-    "//ios/testing:block_swizzler",
-  ]
-}
-
 source_set("perf_test_support") {
   configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true