Updated broken URLs. Fixes #72.

[malloryfreeberg]

Description

• Fixed majority of broken URLs (mostly caused by EGA and GA4GH relaunching their websites) listed in Issue [BUG]: Broken links #72.
• Did not fix a broken Beacon-related URL. All the Beacon info needs to be updated and should be done in a separate PR.
• Did not fix the https://ega.ebi.ac.uk:8052/elixir/tickets/tickets link as this is meant to be a call to our data distribution API endpoints directly, which current we don't have documentation for.

Motivation and Context

It's important to have working URLs!

How has this been tested?

Updated URLs were tested in Google Chrome.

What should reviewers focus on?

Do the URLs also work for the reviewer.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New content (non-breaking change which adds new content)
• Modified content (non-breaking change which modifies existing content)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• I have read the CONTRIBUTING.md guide.
• My changes follow the code style of this project.
• I have updated supporting documentation, if required.
• I have added my details to the CONTRIBUTORS.yaml file.

[M-casado]

Links LGTM 👍