fixed boolean check to use correct flag

A change was made to the validation script and this PR fixes an introduced bug.

pluginEnabled is a string provided to script as ayes/y or no/n argument isPluginEnabled is the boolean derived which should be used in the script.

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[ ] I attest that the connector doesn't exist on the Power Platform today. I've verified by checking the pull requests in GitHub and by searching for the connector on the platform or in the documentation.
[ ] I attest that the connector works and I verified by deploying and testing all the operations.
[ ] I attest that I have added detailed descriptions for all operations and parameters in the swagger file.
[ ] I attest that I have added response schemas to my actions, unless the response schema is dynamic.
[ ] I validated the swagger file, apiDefinition.swagger.json, by running paconn validate command.
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microsoft / PowerPlatformConnectors