Update "Provider cmdlets" for readability

[matt9ucci]

PR Summary

• Remove redundant and less informative qualifiers for methods
• Apply list format for methods
• Remove the level 2 header ## Provider Cmdlets (refrain of the title)
• Level 3 headers -> level 2
• Windows PowerShell -> PowerShell
• Remove meaningless character: *
• Remove duplicates: Invokedefaultaction
• Fix capitalization

PR Context

Conceptual content

• Scripting and development
  • Language Spec
  • Legacy SDK

PR Checklist

• I have read the contributors guide and followed the style and process guidelines
• PR has a meaningful title
• PR is targeted at the staging branch
• This PR is ready to merge and is not Work in Progress

[opbld32]

Docs Build status updates of commit ed52ddf:

✅ Validation status: passed

File	Status	Preview URL	Details
reference/docs-conceptual/developer/provider/provider-cmdlets.md	✅Succeeded	View (>=powershell-5.1)

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[sdwheeler]

Nice cleanup. Thanks.