docs: update formula and cask URLs to new sharded format

[zgracem]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
  • Yes, and I found docs: Add /Formula/* sharding #15891, but was advised to open this anyway.
• Have you added an explanation of what your changes do and why you'd like us to include them?
• [N/A] Have you written new tests for your changes? Here's an example.
• [N/A] Have you successfully run brew style with your changes locally?
• [N/A] Have you successfully run brew typecheck with your changes locally?
• [N/A] Have you successfully run brew tests with your changes locally?

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I was reading through Homebrew's documentation yesterday and noticed that links into the source tree were broken because of the recent reorganization into alphabetized subdirectories. So I searched docs/*.md with the regex /homebrew-(cask|core)/blob/\w+/(Formula|Casks)/[^/]+?\.rb and:

• Links to HEAD were changed to add the single-char subdirectory to the path. Easy peasy.
• Links to specific lines of code at specific commits were updated in different ways:
  • If the code still existed in the same file, the URL was updated to its most recent commit (as of 22 August 2023) and the line numbers were updated if necessary.
  • If the file no longer contained relevant example code, or had been deleted, the link was updated to point to a similar file that does, at that new file's most recent commit (as of 22/8/23). If the link had an adjacent line or three of code in the doc itself, I updated that code from the new file... if I noticed it.
• A handful of links were so old that the code they referenced has been deprecated and removed from Homebrew altogether; no current examples remain (or, presumably, are required). Those links I left unchanged, to be picked up in future substantive edits to the docs' content.

I hope this is a helpful addition to the work in #15891. Please let me know if you have any questions.

[MikeMcQuaid]

Looks good to me so far, nice work @zgracem!

[Bo98]

Thanks!