Adjust TYPO3 docs urls

https://docs.typo3.org/typo3cms/extensions/core/Changelog/7.4/Breaking-68001-RemovedExtJSCoreAndExtJSAdapters.html => https://docs.typo3.org/typo3cms/extensions/core/7.6/Changelog/7.4/Breaking-68001-RemovedExtJSCoreAndExtJSAdapters.html (adding /7.6/path segment)