Update compatible hardware in zigpy-xbee

[Hedda]

Update list of compatible hardware to zigpy-xbee README.md as the plan is to remove such a list from zigpy in https://github.com/zigpy/zigpy/pull/705

Downstream project(s) also want such information to be provided by upstream as per https://github.com/home-assistant/home-assistant.io/pull/17089

[coveralls]

Pull Request Test Coverage Report for Build 326

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 99.721%

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Totals
Change from base Build 325:	0.0%
Covered Lines:	715
Relevant Lines:	717

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💛 - Coveralls