sdbusplus: avoid deprecated phosphor::Timer

sdbusplus had an older type named `phosphor::Timer` which was
recently renamed to `sdbusplus::Timer`.  Update the code to use
the new type alias.

Change-Id: I9a57a056eb7bb38a851f835d573c4271c4a69a0d
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/src/post_code.cpp b/src/post_code.cpp
index ddabf30..957c7ba 100644
--- a/src/post_code.cpp
+++ b/src/post_code.cpp
@@ -76,7 +76,7 @@
 {
     if (!timer)
     {
-        timer = std::make_unique<phosphor::Timer>(
+        timer = std::make_unique<sdbusplus::Timer>(
             event.get(), [this]() { serialize(postCodeListPath); });
     }