desktop-browsers: Update Brave configuration and apply writing style to criteria

[redoomed1]

Changes proposed in this PR:

• Update the guidance for Extensions in the Brave configuration
  • The most recent Brave update enables the "Media Router" extension by default on new profiles. I figure that simplifying the guidance (similar to "Uncheck all social media components") is more desirable than listing the settings to disable because it'll lead to fewer revisions to this section if Brave adds or enables more extensions in the future.
• Apply specific guidance about the language for requirements from the Writing Style page to the criteria for desktop browsers
• Italicize names of settings (settings to be changed remain bolded)

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