Get-PoshThemes no longer exists

[wsmelton]

The steps for configuring a theme have the first step as being able to use Get-PoshThemes to list out the available themes. This command does not exists in the module (has not for a while I believe).

This should instead point users to browse the themes on the module's site here

---

Document Details

⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.

• ID: d3cbeb9a-9e7c-f8f4-5c03-5d6262d2b440
• Version Independent ID: eb575c79-5b2a-45f6-646f-9d41d5d223e8
• Content: Windows Terminal Custom Prompt Setup
• Content Source: TerminalDocs/tutorials/custom-prompt-setup.md
• Product: dev-environment
• Technology: windows-terminal
• GitHub Login: @cinnamon-msft
• Microsoft Alias: cinnamon

[zadjii-msft]

(closed in #505)