Remove unused variable

Change-Id: I927fcd600da43e62a99acefae7ce6afafd6fad8c
Reviewed-on: https://weave-review.googlesource.com/1245
Reviewed-by: Vitaly Buka <vitalybuka@google.com>

libweave/src/weave_unittest.cc

diff --git a/libweave/src/weave_unittest.cc b/libweave/src/weave_unittest.cc
index ac6f9b8..f0f8a58 100644
--- a/libweave/src/weave_unittest.cc
+++ b/libweave/src/weave_unittest.cc
@@ -40,8 +40,6 @@
 using provider::test::MockHttpClientResponse;
 using provider::Network;
 
-const char kCategory[] = "powerd";
-
 const char kCommandDefs[] = R"({
   "base": {
     "reboot": {},