spdlogger: Remove unused headers

This also avoids a Windows linker error when trying to simplify the
usage of phosphor:

   spdlogger.cc.obj : error LNK2019: unresolved external symbol "public: __cdecl phosphor::ChunkLock::ChunkLock ..."

Change-Id: I87163c6e9663910a31a8aab77040c43aeea388ff
Reviewed-on: http://review.couchbase.org/90744
Tested-by: Build Bot <[email protected]>
Reviewed-by: Tim Bradgate <[email protected]>

Author: daverigby

logger/spdlogger.cc

@@ -23,8 +23,6 @@
 
 #include <memcached/engine.h>
 #include <memcached/extension.h>
-#include <phosphor/phosphor.h>
-#include <platform/processclock.h>
 #include <spdlog/sinks/dist_sink.h>
 #include <spdlog/sinks/null_sink.h>
 #include <spdlog/sinks/stdout_sinks.h>