Updated 184 broken links to handbook index

After the handbook was split into smaller pages by https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/4939 many of the old links needed updating.

Originally fixed one in https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/4944 but did a search and found many more:

Searching 1589 files for "/handbook/#"

.../www-gitlab-com/README.md: 309
310 [frontmatter]: https://about.gitlab.com/handbook/marketing/blog/#frontmatter 311: [Writing Style Guidelines]: https://about.gitlab.com/handbook/#writing-style-guidelines 312 [press releases]: https://about.gitlab.com/press/releases/ 313 [press category]: https://about.gitlab.com/blog/categories/press

.../www-gitlab-com/source/about/index.html.md: 83 ## Values 84
85: Please see the values section in our handbook. 86
87 ## Our stewardship of GitLab CE

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184 matches across 102 files

mentioned in merge request !4944 (closed)

@kirstenabma Can you review this?

I haven't tested the links as there are so many of them, but most should be correct unless they were already broken.

assigned to @kirstenabma

added 1 commit

• 8b9b265e - Updated 184 broken links to handbook index

Compare with previous version

assigned to @sytses

mentioned in commit 9eb9ebf6

merged