fix(hreflang): Updating hreflang implemenation

Step 1: What is changing in this MR?

Most globalised URLs no longer contain the correct or are missing hreflang implementation since the CMS migration. These changes occurred October 19 - Nov 3, 2023

Common errors include:

1. Self-referencing hreflang not present - the hreflang implementation needs to specify both the preferred audience for the page itself, and its translated variants
2. Include non-region hreflang alternatives to target language speakers in multiple locations. For example German speakers in Switzerland.
3. Remove data-hid="i18n-alt-de-de" from the implementation. This must be formatted <link rel=”alternate” hreflang=”x” href=”https://example.com/alternate-page” /> with no additional code.
4. Ensure that previously broken hreflang urls are fixed for translated and untranslated pages

• Non-language examples with broken hreflang URLs previously

• https://about.gitlab.com/jobs/
• https://about.gitlab.com/events/
• https://about.gitlab.com/topics/ci-cd/
• https://about.gitlab.com/resources/
• https://about.gitlab.com/topics/version-control/what-is-gitlab-flow/

• Language variants with previously broken hreflang URLs (fr and de):

• https://about.gitlab.com/fr-fr/free-trial/
• https://about.gitlab.com/de-de/solutions/continuous-integration/
• https://about.gitlab.com/de-de/
• https://about.gitlab.com/ja-jp/sales/
• https://about.gitlab.com/fr-fr/solutions/devops-platform/

Production	Review app
https://about.gitlab.com/	https://hreflang-update.about.gitlab-review.app/
https://about.gitlab.com/jobs/	https://hreflang-update.about.gitlab-review.app/jobs/
https://about.gitlab.com/events/	https://hreflang-update.about.gitlab-review.app/events/
https://about.gitlab.com/topics/ci-cd/	https://hreflang-update.about.gitlab-review.app/topics/ci-cd/
https://about.gitlab.com/resources/	https://hreflang-update.about.gitlab-review.app/resources/
https://about.gitlab.com/topics/version-control/what-is-gitlab-flow/	https://hreflang-update.about.gitlab-review.app/topics/version-control/what-is-gitlab-flow/
https://about.gitlab.com/fr-fr/free-trial/	https://hreflang-update.about.gitlab-review.app/fr-fr/free-trial/
https://about.gitlab.com/de-de/solutions/continuous-integration/	https://hreflang-update.about.gitlab-review.app/de-de/solutions/continuous-integration/
https://about.gitlab.com/de-de/	https://hreflang-update.about.gitlab-review.app/de-de/
https://about.gitlab.com/ja-jp/sales/	https://hreflang-update.about.gitlab-review.app//ja-jp/sales/
https://about.gitlab.com/fr-fr/solutions/devops-platform/	https://hreflang-update.about.gitlab-review.app/fr-fr/solutions/devops-platform/

Step 2: Ensure that your changes comply with the following, where applicable:

• I, the Assignee, have run Axe tools on any updated pages, and fixed the relevant accessibility issues.
• These changes work on both Safari, Chrome, and Firefox.
• These changes have been reviewed for Visual Quality Assurance and Functional Quality Assurance on Mobile, Desktop, and Tablet.
• These changes work with our Google Analytics and SEO tools.
• These changes have been documented as expected.

Build Variables:

• Use Contentful Preview API