Gradle task spotlessInternalRegisterDependencies configured eagerly

[3flex]

When running ./gradlew help --scan the Build Scan reports task spotlessInternalRegisterDependencies is configured. Gradle's task configuration avoidance feature should be used so it's only configured when needed.

Affects spotless on main branch. The problem was introduced by #1039, thanks to get() call here:

spotless/plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessExtension.java

Line 52 in f4ee554

this.registerDependenciesTask = findRegisterDepsTask().get();