minor #15869 Deleting incomplete components page (ThomasLandauer)

This PR was merged into the 4.4 branch.

Discussion
----------

Deleting incomplete components page

`@wouterj` You told me at #14194 (comment) that this list is going to be merged into https://symfony.com/components , so this here is obsolete, right?
Should I double-check for every component and add them to the other list if needed?

Commits
-------

084dec6 Deleting incomplete components page

Author: javiereguiluz