Remove the use of Shared to describe GitLab SaaS Runners

Step 1: What is changing in this MR?

Removing the use of the term Shared to describe the GitLab.com SaaS Runners offer.

It includes the renamings on the pricing page for:

• shared to instance runners
• SaaS runners to Hosted runners
• GitLab SaaS to GitLab.com

Related issue:

• https://gitlab.com/gitlab-com/Product/-/issues/13130+s
• Rename SaaS runners to Hosted runners (gitlab-com/Product#13113 - closed) • Fiona Neill, Rebecca Clayman+

Production	Review app
https://about.gitlab.com/	WIP

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.