#431, Add ostruct as a dependency to the gemspec

This commit adds `ostruct` as an explicit dependency
in the net-ldap gemspec.

With the release of Ruby 3.3.5 and later versions,
users of net-ldap may encounter warnings related
to the use of `ostruct` if it is not declared as
a dependency. By including `ostruct`, we aim to
enhance clarity regarding the gem's requirements
and prevent any runtime issues related to missing
dependencies.

Author: Ivanov-Anton

Diff for: net-ldap.gemspec

@@ -29,6 +29,7 @@ the most recent LDAP RFCs (4510-4519, plutions of 4520-4532).}
   s.required_ruby_version = ">= 2.0.0"
   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_dependency("ostruct")
   s.add_development_dependency("flexmock", "~> 1.3")
   s.add_development_dependency("rake", "~> 12.3.3")
   s.add_development_dependency("rubocop", "~> 1.48")