Update VS Code instructions for creating a prompt file #46305

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://docs.github.com/en/copilot/how-tos/copilot-in-your-ide/customize-copilot/configure-custom-instructions/add-repository-instructions-in-your-ide?tool=vscode#creating-prompt-files

What part(s) of the article would you like to see updated?

In the Creating prompt files section, the article currently instructs users to type prompt and select Chat: Create Prompt in VS Code.

However, in the current VS Code interface, the command is named Chat: New Prompt File, not Chat: Create Prompt.

Additional information

Update the instructions to reflect the current command name so users can follow the steps accurately.