Removes nl2br from the text documentation

The documentation for the text extensions still refers to the
nl2br tag, which has been removed from extensions and added to
the main Twig repo. This commit removes the mention of nl2br
from this repo.
minor #118 Removes nl2br from the text documentation (enkrates)

This PR was merged into the 1.1.x-dev branch.

Discussion
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Removes nl2br from the text documentation

The documentation for the text extensions still refers to the
nl2br tag, which has been removed from extensions and added to
the main Twig repo. This commit removes the mention of nl2br
from this repo.

Commits
-------

9af0ed4 Removes nl2br from the text documentation