Remove unused namespace

After some recent changes, the error.hpp file must be included to find
sdbusplus::xyz::openbmc_project::Common::Error, but it's unused, so just
remove it.

Change-Id: I185c453def4515a35749f687a57b4f0b6da6deb8
Signed-off-by: Jason M. Bills <jason.m.bills@intel.com>
diff --git a/src/allowlist-filter.cpp b/src/allowlist-filter.cpp
index 4883b52..acf423c 100644
--- a/src/allowlist-filter.cpp
+++ b/src/allowlist-filter.cpp
@@ -9,7 +9,6 @@
 #include <array>
 
 using namespace phosphor::logging;
-using namespace sdbusplus::xyz::openbmc_project::Common::Error;
 using namespace sdbusplus::xyz::openbmc_project::Control::Security::server;
 
 namespace ipmi