Double check keystore user messages

[ChristopherDedominici]

Check that the messages are following the Hardhat design rules.

E.g.:

• message to setup the keystore
• messages that show commands to run

[Tmthang1601]

Hi @ChristopherDedominici,

I've created a Pull Request to address this issue:

In this PR, I've made the following improvements: #5750

1. Refactored the deprecation warning message in cli.ts to be more concise and clear.
2. Updated task descriptions in getting-started/index.md for better consistency.
3. Clarified the 'check' task description in check.ts.
4. Added an example of running a task with a network parameter in the tasks.md guide.

These changes aim to improve the overall consistency and clarity of Hardhat's messages and documentation, following the Hardhat design rules. I've paid special attention to:

• Ensuring messages for setting up the keystore are clear and concise.
• Improving the clarity of messages that show commands to run.

I would appreciate your review and feedback on these changes. Please let me know if any further modifications are needed.

Thank you for bringing this issue to attention!