unit_tests: do not rethrow a copy of an exception

Found by codacy.com

tests/unit_tests/subaddress.cpp

@@ -49,7 +49,7 @@ class WalletSubaddress : public ::testing::Test
       catch (const std::exception& e)
       {
         LOG_ERROR("failed to generate wallet: " << e.what());
-        throw e;
+        throw;
       }
 
       w1.add_subaddress_account(test_label);