[AFE-46] use Astronomer releases endpoint for version checking

[nickypy]

Description

This PR replaces the GitHub release check to use https://updates.astronomer.io/astro-cli instead. This matches the behavior in Astro UI and takes into account the delay between release in this repo vs Homebrew.

🎟 Issue(s)

Fixes #1977

🧪 Functional Testing

VERSION=1.38 make build
./astro version

📸 Screenshots

Add screenshots to illustrate the validity of these changes.

📋 Checklist

• Rebased from the main (or release if patching) branch (before testing)
• Ran make test before taking out of draft
• Ran make lint before taking out of draft
• Added/updated applicable tests
• Tested against Astro-API (if necessary).
• Tested against Houston-API and Astronomer (if necessary).
• Communicated to/tagged owners of respective clients potentially impacted by these changes.
• Updated any related documentation

[coveralls-official]

Pull Request Test Coverage Report for Build d223ff04-db5f-4e21-8565-a8d105d1dce5

Details

• 34 of 44 (77.27%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 35.946%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
version/version.go	30	40	75.0%

Totals
Change from base Build 408796d1-867a-49d6-a9f1-470124cda0c8:	0.03%
Covered Lines:	24318
Relevant Lines:	67652

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💛 - Coveralls