remove unused var

Change-Id: I2efbcf7b17be55d06be581a98b83c400da39d2db
diff --git a/src/ca-module.cpp b/src/ca-module.cpp
index a7c2fdb..bdb0236 100644
--- a/src/ca-module.cpp
+++ b/src/ca-module.cpp
@@ -40,7 +40,6 @@
 
 static const time::seconds DEFAULT_DATA_FRESHNESS_PERIOD = 1_s;
 static const time::seconds REQUEST_VALIDITY_PERIOD_NOT_BEFORE_GRACE_PERIOD = 120_s;
-static const int AES_128_KEY_LEN = 16;
 
 NDN_LOG_INIT(ndncert.ca);