DOC-1061: Update Dropbox credentials to medium tier template

[freakwriter]

Incorporate prerequisites in auth methods, convert short bullet points to detailed numbered lists, provide more guidance on when to use which method and when approval would be required.

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Overall readability score: 43.1 (🟢 +0.02)

File	Readability
dropbox.md	69.73 (🟢 +20.4)

View detailed metrics

🟢 - Shows an _increase_ in readability 🔴 - Shows a _decrease_ in readability File | Readability | FRE | GF | ARI | CLI | DCRS --- | --- | --- | --- | --- | --- | --- [dropbox.md](https://github.com/n8n-io/n8n-docs/blob/f83de72d14a78b24fd213497a1508e4248838bb4/docs/integrations/builtin/credentials/dropbox.md "docs/integrations/builtin/credentials/dropbox.md") | 69.73 | 48.81 | 7.48 | 11.1 | 11.77 | 6.06   | 🟢 +20.4 | 🟢 +13.37 | 🟢 +0.8 | 🟢 +3.3 | 🟢 +4.15 | 🟢 +1.92 Averages:   | Readability | FRE | GF | ARI | CLI | DCRS --- | --- | --- | --- | --- | --- | --- Average | 43.1 | 34.81 | 11.67 | 14.88 | 14.36 | 8.54   | 🟢 +0.02 | 🟢 +0.01 | 🟢 +0 | 🟢 +0 | 🟢 +0 | 🟢 +0

View metric targets

Metric | Range | Ideal score --- | --- | --- Flesch Reading Ease | 100 (very easy read) to 0 (extremely difficult read) | 60 Gunning Fog | 6 (very easy read) to 17 (extremely difficult read) | 8 or less Auto. Read. Index | 6 (very easy read) to 14 (extremely difficult read) | 8 or less Coleman Liau Index | 6 (very easy read) to 17 (extremely difficult read) | 8 or less Dale-Chall Readability | 4.9 (very easy read) to 9.9 (extremely difficult read) | 6.9 or less