Remove FileSystemFlags dictionary from MDN web docs

[queengooborg]

This PR removes the FileSystemFlags dictionary from MDN web docs, folding its content into the pages that utilize it. Correlates with its removal in BCD, see mdn/browser-compat-data#12766.

This PR performs some additional changes to the data for formatting and flow. Namely, the table is now converted to Markdown, and wording has been updated to refer to what happens for files and directories on their respective pages.

[github-actions]

Preview URLs

• https://pr10920.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/FileSystemDirectoryEntry/getDirectory
• https://pr10920.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/FileSystemDirectoryEntry/getFile
• https://pr10920.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/File_and_Directory_Entries_API

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/API/File_and_Directory_Entries_API
Title: File and Directory Entries API
on GitHub

• https://bugzilla.mozilla.org/show_bug.cgi?id=1326031 (1 time)

---

URL: /en-US/docs/Web/API/FileSystemDirectoryEntry/getFile
Title: FileSystemDirectoryEntry.getFile()
on GitHub

No new external URLs

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URL: /en-US/docs/Web/API/FileSystemDirectoryEntry/getDirectory
Title: FileSystemDirectoryEntry.getDirectory()
on GitHub

No new external URLs