package/agentpp: fix broken URL in help text

The curren URL is specific to an old version, and it is not reachable
anymore.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/agentpp/Config.in

@@ -16,7 +16,7 @@ config BR2_PACKAGE_AGENTPP
 
 	  SNMPv3 support is enabled if SNMP++ enables it.
 
-	  http://www.agentpp.com/agentpp3_5/agentpp3_5.html
+	  https://www.agentpp.com/api/cpp/agent_pp.html
 
 comment "agent++ needs a toolchain w/ threads, C++, dynamic library"
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS || \