socket.h: removing dependency of gtest

Removed the dependency of gtest on the build of fastboot binary.
Fixes below error

In file included from fastboot/fastboot.cpp:70:
| In file included from fastboot/tcp.h:36:
| fastboot/socket.h:43:10: fatal error: 'gtest/gtest_prod.h' file not found
| #include <gtest/gtest_prod.h>
|          ^~~~~~~~~~~~~~~~~~~~
| 1 error generated.
| In file included from fastboot/socket.cpp:29:
| fastboot/socket.h:43:10: fatal error: 'gtest/gtest_prod.h' file not found
| #include <gtest/gtest_prod.h>
|          ^~~~~~~~~~~~~~~~~~~~
| 1 error generated.
| In file included from fastboot/tcp.cpp:29:
| In file included from fastboot/tcp.h:36:
| fastboot/socket.h:43:10: fatal error: 'gtest/gtest_prod.h' file not found
| #include <gtest/gtest_prod.h>
|          ^~~~~~~~~~~~~~~~~~~~
| 1 error generated.
| In file included from fastboot/udp.cpp:31:
| In file included from fastboot/udp.h:34:
| fastboot/socket.h:43:10: fatal error: 'gtest/gtest_prod.h' file not found
| #include <gtest/gtest_prod.h>
|          ^~~~~~~~~~~~~~~~~~~~
| 1 error generated.


Signed-off-by: Nisha Parrakat <Nisha.Parrakat@kpit.com>

--- a/system/core/fastboot/socket.h       2021-04-14 21:14:00.355973915 +0000
+++ b/system/core/fastboot/socket.h   2021-04-14 21:14:21.879680699 +0000
@@ -40,7 +40,6 @@

 #include <android-base/macros.h>
 #include <cutils/sockets.h>
-#include <gtest/gtest_prod.h>

 // Socket interface to be implemented for each platform.
 class Socket {
@@ -119,8 +118,6 @@
             socket_send_buffers_function_ = &socket_send_buffers;

   private:
-    FRIEND_TEST(SocketTest, TestTcpSendBuffers);
-    FRIEND_TEST(SocketTest, TestUdpSendBuffers);

     DISALLOW_COPY_AND_ASSIGN(Socket);
 };