WebView: Remove unused reference to storage::QuotaClient.

This will avoid including this file in a large CL that turns QuotaClient
into a mojo interface.

Bug: 1016065
Change-Id: If029b5362fcc77b7acf8e55206b7143900ff6369
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2501062
Commit-Queue: Changwan Ryu <changwan@chromium.org>
Auto-Submit: Victor Costan <pwnall@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821271}

android_webview/browser/aw_quota_manager_bridge.cc

@@ -29,7 +29,6 @@ using base::android::JavaParamRef;
 using base::android::ScopedJavaLocalRef;
 using content::BrowserThread;
 using content::StoragePartition;
-using storage::QuotaClient;
 using storage::QuotaManager;
 
 namespace android_webview {