[ios] Remove unnecessary import from testing/iossim/BUILD.gn

The two imports are unnecessary as none of the variables that
are defined in the imported files is used. Remove the imports
since they are not useful.

Bug: none
Change-Id: Id6d87ed3c43a4804a87161e48241d2f945c3ba92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2471417
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817085}

testing/iossim/BUILD.gn

@@ -2,9 +2,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build/config/ios/ios_sdk.gni")
-import("//build/config/mac/mac_sdk.gni")
-
 if (current_toolchain == host_toolchain) {
   executable("iossim") {
     sources = [ "iossim.mm" ]