The 'samples/apply-on-subproject-sample' do not work

[finnlander]

Describe the bug

The multi-project setup does not seem to work according to the provided sample.

To Reproduce
When cloning this repository and running:

cd semantic-version-gradle-plugin/samples/apply-on-subproject-sample
./gradlew build

... the following error appears:

(some output omitted here)
* What went wrong:
A problem occurred evaluating project ':child1'.
> Failed to apply plugin 'com.dipien.semantic-version'.
   > The Semantic Version Gradle plugin must be applied only on the root project
(some output omitted here)

Expected behavior
Based on the multi-module setup, it should be possible to increase sub-project version (I'd assume as there's the sample available).