Enhance installation instructions for custom location

[yujiaoMSFT]

Added recommendations for using the Deployment Tool for easier onboarding and clarified installation steps for the installer script.

[prmerger-automator]

@yujiaoMSFT : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit 646c2fe:

⚠️ Validation status: warnings

File	Status	Preview URL	Details
defender-endpoint/linux-custom-location-installation.md	⚠️Warning		Details

defender-endpoint/linux-custom-location-installation.md

• Line 67, Column 178: [Warning: hard-coded-locale - See documentation] Link 'https://learn.microsoft.com/en-us/defender-endpoint/linux-install-with-defender-deployment-tool' contains locale code 'en-us'. For localizability, remove 'en-us' from links to most Microsoft sites.
• Line 192, Column 6: [Warning: hard-coded-locale - See documentation] Link 'https://learn.microsoft.com/en-us/defender-endpoint/linux-install-with-defender-deployment-tool' contains locale code 'en-us'. For localizability, remove 'en-us' from links to most Microsoft sites.
• Line 67, Column 178: [Suggestion: docs-link-absolute - See documentation] Absolute link 'https://learn.microsoft.com/en-us/defender-endpoint/linux-install-with-defender-deployment-tool' will be broken in isolated environments. Replace with a relative link.
• Line 192, Column 6: [Suggestion: docs-link-absolute - See documentation] Absolute link 'https://learn.microsoft.com/en-us/defender-endpoint/linux-install-with-defender-deployment-tool' will be broken in isolated environments. Replace with a relative link.

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