Update 07-Customizing-Contao.md

Based on Contao 3.2.7

Removed Hooks:
1. loadFormField
2. processFormData
3. validateFormField

Added Hooks:
1. generateXmlFiles
2. getArticle
3. getAttributesFromDca
4. getCacheKey
5. getCombinedFile
6. getCountries
7. getForm
8. getFrontendModule
9. getRootPageFromUrl
10. getSystemMessages
11. getUserNavigation
12. indexPage
13. insertTagFlags
14. isAllowedToEditComment
15. isVisibleElement
16. modifyFrontendPage
17. parseArticles
18. parseTemplate
19. parseWidget
20. replaceDynamicScriptTags
21. setCookie
22. sqlCompileCommands
23. sqlGetFromDB
24. sqlGetFromDca
25. sqlGetFromFile
26. updatePersonalData