Refactor community/guidelines/release-guidelines

[IwonaLanger]

The community/guidelines/release-guidelines are obsolete as part of the monolithic Kyma documentation before introducing modules. We have to:

• Remove the obsolete release guidelines
• Create a new document on the OS release process
• Include all internal documents on the release process in the internal repository

[mmitoraj]

@zhoujing2022 confirmed we can remove the guidelines as obsolete. See this comment. Instead, we will create one document on the OS Release Process linking to modules' release documentation.