[gradle] fix local engine property name

[jonahwilliams]

I would recommend changing the propety mock so that the properties are given as strings and not constants, otherwise you can run into problems like this where the mock does exactly what you want :)

[flutter-dashboard]

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[gmackall]

LGTM, sorry for the disruption. Oh how I wish we could actually test a real gradle Project object instead of testing mockk endlessly

[jonahwilliams]

No worries. You'd think we'd have a test for this by now.

[auto-submit]

autosubmit label was removed for flutter/flutter/165444, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label.