timer: remove deprecated phosphor namespace

All known uses of the phosphor::Timer have been removed from the
codebase so we can remove this alias.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I894bd3d340a0812254e9c092f3734b3c208bfb2e
diff --git a/include/sdbusplus/timer.hpp b/include/sdbusplus/timer.hpp
index 2127189..3695494 100644
--- a/include/sdbusplus/timer.hpp
+++ b/include/sdbusplus/timer.hpp
@@ -247,9 +247,3 @@
 };
 
 } // namespace sdbusplus
-
-namespace phosphor
-{
-// Deprecated name alias.
-using sdbusplus::Timer;
-} // namespace phosphor