cmake: Remove the private tag from the openssl requirement

- It's trigging a Conan bug with software that uses libxml2, such as
  PDFAlchemist.

- The problem is that the private requirement is skipped, and there's no
  cpp_info, and that's not checked when doing an internal Conan
  conversion.

See: conan-io/conan#10439

recipes/cmake/3.x.x/conanfile.py

@@ -35,7 +35,7 @@ def config_options(self):
 
     def requirements(self):
         if self.options.with_openssl:
-            self.requires("openssl/1.1.1s", private=True)
+            self.requires("openssl/1.1.1s")
 
     def validate(self):
         if self.settings.os == "Macos" and self.settings.arch == "x86":