Update event log section in README.md

Display the full namespace of metadata in the example

Change-Id: I47ead58878320975b6c2c024a5028f16fae5026b
Signed-off-by: Daniel Hsu <Daniel-Hsu@quantatw.com>
diff --git a/README.md b/README.md
index c56b72e..0537825 100644
--- a/README.md
+++ b/README.md
@@ -149,7 +149,7 @@
 using WriteFailure =
     sdbusplus::xyz::openbmc_project::Control::Device::Error::WriteFailure;
 using metadata =
-    xyz::openbmc_project::Control::Device::WriteFailure;
+    phosphor::logging::xyz::openbmc_project::Control::Device::WriteFailure;
 ...
 if (somethingBadHappened)
 {