* throw an error if a page is available in a version that its parent product is not available in
* add tests
* fix one Insights content file versioned for FPT when Insights is only available in GHES currently
* remove FEATURE_NEW_VERSIONS from feature-flags.json
* remove process.env.FEATURE_NEW_VERSIONS from include files
* remove process.env.FEATURE_NEW_VERSIONS from lib files
* remove process.env.FEATURE_NEW_VERSIONS from middleware files
* remove process.env.FEATURE_NEW_VERSIONS from script files
* remove process.env.FEATURE_NEW_VERSIONS from test files
* update test fixtures to use new versions as canonical fixtures