Doc: Remove nonexistent qtwebkitwidgets reference

There is no such qtwebkitwidgets.index file to be used in \depends

Change-Id: I191801d22d908721e8d65b610f684c23b7dc7870
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Doc: Fix most of the documentation warnings

- adding missing index files to \depends
- fix warning: Can't link to 'The QtWebKit Bridge'

Change-Id: I60665627f1aadbf7bd8a20ddda7d22db9ad694dc
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>