Update carbon emissions methodology page to match current feature spe…

[Renni771]

Addresses #15046. Admin configuration options were added in PR #16307. This PR update the methodology page to match the current implementation spec, in particular how admins configure the server's geographical location and how the carbon intensity value used in the calculations corresponds to that value. This PR also mentions how admins can set custom PUE values and how these values are used in the calculations.

What else changed/fixed:

• Typos.
• Some sentences were reworded.
• The old spec mentioned that server hardware information is used when provided. Galaxy doesn't support this right now, so I took that out and mentioned that to the users for transparency. I also explain how we use AWS estimates since the current implementation is based solely on that.

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.

[bgruening]

Thanks @Renni771

[github-actions]

This PR was merged without a "kind/" label, please correct.