Delete unused proguard_config_exclusions variable.

Bug: 866937
Change-Id: Ifc6e7824491f6b89de24d97800852d2288cc9d28
Reviewed-on: https://chromium-review.googlesource.com/1148565Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577825}

chrome/android/BUILD.gn

@@ -1509,8 +1509,6 @@ if (enable_arcore && package_arcore) {
     proguard_enabled = !is_java_debug
     if (proguard_enabled && !enable_proguard_obfuscation) {
       proguard_configs = [ "//base/android/proguard/enable_obfuscation.flags" ]
-      proguard_config_exclusions =
-          [ "//base/android/proguard/disable_chromium_obfuscation.flags" ]
     }
     alternative_android_sdk_dep = webview_framework_dep