Wrong parent/version in /core

### Expected Behaviour
reference in submodules should be the one defined in the YAML definition under repositoryModernizer/version

### Actual Behaviour
Define version is used in parent pom and in the back reference for each module EXCEPT for core, where it is statically set to 1.0-SNAPSHOT

### Reproduce Scenario (including but not limited to)

#### Steps to Reproduce
- set repositoryModernizer/version to 5.0-SNAPSHOT
- run modernizer
- check parent version in core/pom.xml

#### Platform and Version
- macos
- node 12
- @adobe/aio-cli-plugin-aem-cloud-service-migration 1.2.3

#### Sample Code that illustrates the problem

#### Logs taken while reproducing problem

Start by inspecting core/pom.xml and the handling of repositoryModernizer/version in the modernizer. Reproduce the issue by setting the version to 5.0-SNAPSHOT and running the modernizer, then verify that core/pom.xml uses the configured parent and module-back-reference version rather than 1.0-SNAPSHOT.

Written by the indexing model from the issue text.