Fix: don't generate 1-parameter tests for mutually exclusive parameters.

[dblock]

Fixes the generator specs failing in #524

[dangerpr-bot]

	1 Warning
⚠️	Unless you're refactoring existing code or improving documentation, please update CHANGELOG.md.

Here's an example of a CHANGELOG.md entry:

* [#529](https://github.com/slack-ruby/slack-ruby-client/pull/529): Fix: don't generate 1-parameter tests for mutually exclusive parameters - [@dblock](https://github.com/dblock).

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[github-actions]

Pull Request Test Coverage Report for Build 12106245390

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Details

• 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 89.336%

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Totals
Change from base Build 11729882498:	0.0%
Covered Lines:	5395
Relevant Lines:	6039

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