update model_fixes.js to set CardAction.channelData as an optional property

[stevengum]

First fix for #639

Description

Add "channelData" as an optional property for the CardAction interface.

Note: This doesn't fix #639 directly as the library needs to be regenerated. This PR sets it up so that then the library is properly regenerated (via the generateClient scripts), #639 will be fixed.

[stevengum]

Pinging @sgellock as FYI

[coveralls]

Pull Request Test Coverage Report for Build 2239

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.06%) to 82.098%

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Files with Coverage Reduction	New Missed Lines	%
libraries/botframework-config/src/botConfigurationBase.ts	2	85.59%

Totals
Change from base Build 2217:	-0.06%
Covered Lines:	2633
Relevant Lines:	3088

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💛 - Coveralls