Docs: make the Emoji cheat sheet links consistent

What does this MR do and why?

This MR makes the Emoji cheat sheet links consistent between the visible code snippet and the actual markdown source in GitLab Flavored Markdown.

Previously, the visible code snippet claimed to link to a list of emoji codes, but instead linked to https://www.emojicopy.com/ which doesn't actually contain these codes. The actual rendered markdown correctly linked to https://www.webfx.com/tools/emoji-cheat-sheet/, so in this MR I simply made the code snippet use the same link as well. I myself first went to the wrong link to look for Emoji codes, and was confused as to where they were.

Related issues

Author's checklist

• Optional. Consider taking the GitLab Technical Writing Fundamentals course.
• Follow the:
  • Documentation process.
  • Documentation guidelines.
  • Style Guide.
• Not applicable If you're adding or changing the main heading of the page (H1), ensure that the product tier badge is added.
• Not applicable If you are a GitLab team member, request a review based on:
  • The documentation page's metadata.
  • The associated Technical Writer.

If you are a GitLab team member and only adding documentation, do not add any of the following labels:

• ~"frontend"
• ~"backend"
• ~"type::bug"
• ~"database"

These labels cause the MR to be added to code verification QA issues.

Reviewer's checklist

Documentation-related MRs should be reviewed by a Technical Writer for a non-blocking review, based on Documentation Guidelines and the Style Guide.

If you aren't sure which tech writer to ask, use roulette or ask in the #docs Slack channel.

• If the content requires it, ensure the information is reviewed by a subject matter expert.
• Technical writer review items:
  • Ensure docs metadata is present and up-to-date.
  • Ensure the appropriate labels are added to this MR.
  • Ensure a release milestone is set.
  • If relevant to this MR, ensure content topic type principles are in use, including:
    • The headings should be something you'd do a Google search for. Instead of Default behavior, say something like Default behavior when you close an issue.
    • The headings (other than the page title) should be active. Instead of Configuring GDK, say something like Configure GDK.
    • Any task steps should be written as a numbered list.
    • If the content still needs to be edited for topic types, you can create a follow-up issue with the docs-technical-debt label.
• Review by assigned maintainer, who can always request/require the reviews above. Maintainer's review can occur before or after a technical writer review.