update format of doxygen

Change-Id: I52abc25afb46df4ac010b5251b123a6c1be2434b
diff --git a/src/configuration.hpp b/src/configuration.hpp
index 8a1d037..c881786 100644
--- a/src/configuration.hpp
+++ b/src/configuration.hpp
@@ -85,7 +85,7 @@
  * fired whenever a request instance is created, challenge status is updated, and when certificate
  * is issued.
  *
- * @p CaState, input, the state of the certificate request whose status is updated.
+ * @param CaState The state of the certificate request whose status is updated.
  */
 using StatusUpdateCallback = function<void(const CaState&)>;