guideline: remove 'using namespace' from headers

Using namespace at global scope in a header file violates the cpp core
guidelines.  Quoting the guidelines:

  "Doing so takes away an #includer’s ability to effectively
disambiguate and to use alternatives. It also makes #included headers
order-dependent as they might have different meaning when included in
different orders."

For further reading:
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rs-using-directive

Change-Id: I40fd6b31a94fe9a12426f76fc71d0832125a8740
Signed-off-by: Pavithra Barithaya <pavithra.b@ibm.com>
diff --git a/settings.hpp b/settings.hpp
index a61cae7..0753e1e 100644
--- a/settings.hpp
+++ b/settings.hpp
@@ -11,8 +11,6 @@
 namespace settings
 {
 
-using namespace phosphor::time::utils;
-
 constexpr auto root = "/";
 constexpr auto timeSyncIntf = "xyz.openbmc_project.Time.Synchronization";
 
@@ -35,7 +33,7 @@
     ~Objects() = default;
 
     /** @brief time sync method settings object */
-    Path timeSyncMethod = DEFAULT_TIME_SYNC_OBJECT_PATH;
+    phosphor::time::utils::Path timeSyncMethod = DEFAULT_TIME_SYNC_OBJECT_PATH;
 };
 
 } // namespace settings