[master] editorial: removed an unnecessary semicolon

commiting at my discretion.

src/lib/dhcpsrv/lease_mgr.h

@@ -117,7 +117,7 @@ struct Lease {
     Lease(const isc::asiolink::IOAddress& addr, uint32_t t1, uint32_t t2,
           uint32_t valid_lft, SubnetID subnet_id, time_t cltt);
 
-    virtual ~Lease() {};
+    virtual ~Lease() {}
 
     /// @brief IPv4 ot IPv6 address
     ///