Clarify docs for destination of dependencyInjection GAVs

[ASzc]

The way the documentation is worded, it makes it sound like -DdependencyInjection adds a real dependency entry to the POMs. In fact it adds a dependencyManagement entry, as seen in the code here:

https://github.com/release-engineering/pom-manipulation-ext/blob/main/core/src/main/java/org/commonjava/maven/ext/core/impl/DependencyInjectionManipulator.java#L95

[rnc]

Thanks!