[23.2] Add hgweb_repo_prefix attribute to TestToolShedConfig

[nsoranzo]

Fix the following error in unit tests:

AttributeError: 'TestToolShedConfig' object has no attribute 'hgweb_repo_prefix'

caused by merging commit b00beec forward.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.