Update libzip info in DeveloperSetupGuide.md

The libzip dependency was upgraded to 1.9.2 here: https://github.com/google/omaha/commit/15fa03a7210263b3a32bb407d878124b78c10b45

However, DeveloperSetupGuide.md still references libzip 1.7.3, with which the project no longer compiles.

Please update the docs to avoid confusion.