Remove ProxyResolver from update_engine

Current ProxyResolver code only supports no-proxy. Therefore it is
barely any use. Remove current implementation for a better one.

Test: th
Bug: 235816007
Change-Id: Ieb46dedf6c6ea86b11c81d7691c2adb578d3d97d
diff --git a/common/mock_http_fetcher.h b/common/mock_http_fetcher.h
index 3d7859b..0d4b130 100644
--- a/common/mock_http_fetcher.h
+++ b/common/mock_http_fetcher.h
@@ -42,10 +42,8 @@
  public:
   // The data passed in here is copied and then passed to the delegate after
   // the transfer begins.
-  MockHttpFetcher(const uint8_t* data,
-                  size_t size,
-                  ProxyResolver* proxy_resolver)
-      : HttpFetcher(proxy_resolver),
+  MockHttpFetcher(const uint8_t* data, size_t size)
+      : HttpFetcher(),
         sent_offset_(0),
         timeout_id_(brillo::MessageLoop::kTaskIdNull),
         paused_(false),
@@ -55,9 +53,8 @@
   }
 
   // Constructor overload for string data.
-  MockHttpFetcher(const char* data, size_t size, ProxyResolver* proxy_resolver)
-      : MockHttpFetcher(
-            reinterpret_cast<const uint8_t*>(data), size, proxy_resolver) {}
+  MockHttpFetcher(const char* data, size_t size)
+      : MockHttpFetcher(reinterpret_cast<const uint8_t*>(data), size) {}
 
   // Cleans up all internal state. Does not notify delegate
   ~MockHttpFetcher() override;