Remove reference to LXDE.

Summary:
Introduction to Lubuntu mentions that Lubuntu team take care of LXDE packages in
LTS releases of Lubuntu. With 18.04 EOL in April 2021, this is no longer the case.

Test Plan: Manual compiles

Reviewers: lynorian

Reviewed By: lynorian

Differential Revision: https://phab.lubuntu.me/D112

source/index.rst

@@ -8,7 +8,9 @@ What is Lubuntu?
 
 The project’s goal is to provide a lightweight yet functional Linux distribution based on a rock-solid Ubuntu base. Lubuntu provides a simple but modern and powerful graphical user interface, and comes with a wide variety of applications so you can browse, email, chat, play, and be productive. Lubuntu was formerly a distribution for low-end hardware, but `we have refocused <https://Lubuntu.me/taking-a-new-direction/>`_.
 
-Members of the team take care of LXQt and other packages that are part of Lubuntu in the Ubuntu archive, as well as the LXDE packages in the LTS releases of Lubuntu. Lubuntu received official recognition as a formal member of the Ubuntu family beginning with Lubuntu 11.10.
+Members of the team take care of LXQt and other packages that are part of Lubuntu in the Ubuntu archive. 
+
+Lubuntu received official recognition as a formal member of the Ubuntu family beginning with Lubuntu 11.10.
 
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