Remove deprecated use of `getConvention` #502

Job	Run time
Sanity checks (17, ubuntu-20.04)	3m 47s
Windows Gradle plugin functional testing	0s
Functional testing (current, current, 17, ubuntu-20.04)	4m 0s
Functional testing (current, 8.0.1, 17, ubuntu-20.04)	3m 18s
Functional testing (7.4, current, 17, ubuntu-20.04)	3m 50s
Functional testing (7.4, 8.0.1, 17, ubuntu-20.04)	4m 38s
	19m 33s

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