[docs] Communicate filterable/aggregable columns as pro feature

[Bharat Kashyap]

• To do:

  • broken link on the Toolpad Pro Plan link
  • rename "paid plan" to "pro plan"
  • add a video describing the grouping and aggregating feature
  • mention Grouping and Aggregation as part of the Pro Plan on the roadmap page, but included within the X Premium License

• Proposal:

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