chore: upgrade rake to 13.x

Author: straggler7

net-ldap.gemspec

@@ -30,7 +30,7 @@ the most recent LDAP RFCs (4510-4519, plutions of 4520-4532).}
   s.summary = %q{Net::LDAP for Ruby (also called net-ldap) implements client access for the Lightweight Directory Access Protocol (LDAP), an IETF standard protocol for accessing distributed directory services}
 
   s.add_development_dependency("flexmock", "~> 1.3")
-  s.add_development_dependency("rake", "~> 10.0")
+  s.add_development_dependency("rake", "~> 13.0")
   s.add_development_dependency("rubocop", "~> 0.42.0")
   s.add_development_dependency("test-unit")
   s.add_development_dependency("byebug")