Improve the upgrade messaging for new releases

[BasPH]

Describe the bug

We postpone new releases to brew for 1 week due to revert challenges. New CLI releases are immediately installable via curl or Astronomer's homebrew tap, but the CLI gives a conflicting message:

A newer version of Astro CLI is available: 1.38.0
Please update to the latest version using 'brew upgrade astro'

We should improve that message while a new release is not available yet on brew.
Slack thread: https://astronomer.slack.com/archives/CL44PA4DB/p1761822268861389

What CLI Version did you experience this bug?

This CLI bug is related to which Astronomer Platform?

• Astro
• Software
• None/Unknown

What Operating System is the above CLI installed on?

🪜 Steps To Reproduce

📸 Screenshots