Merge adb_connection_maintainer into adb_connector

adb_connection_maintainer was not used by any other libraries or
binaries. This consolidates code by removing a directory.

Test: launch_cvd
Change-Id: I49cf074b278e3745ee3a2125af6bb508380a6c5e
diff --git a/host/frontend/adb_connector/main.cpp b/host/frontend/adb_connector/main.cpp
index 3d3d824..a6f8ebe 100644
--- a/host/frontend/adb_connector/main.cpp
+++ b/host/frontend/adb_connector/main.cpp
@@ -28,8 +28,8 @@
 #include <host/commands/kernel_log_monitor/kernel_log_server.h>
 
 #include "common/libs/fs/shared_fd.h"
+#include "host/frontend/adb_connector/adb_connection_maintainer.h"
 #include "host/libs/config/cuttlefish_config.h"
-#include "host/libs/adb_connection_maintainer/adb_connection_maintainer.h"
 
 DEFINE_string(addresses, "", "Comma-separated list of addresses to "
                              "'adb connect' to");