These three commits add <desc> tags to all help files where
they did not exist before.

Also, I include a period (.) at the end of each description.

Finally, removed one help topics that duplicated the info
from another help topic.

docs: Added <desc> descriptions to help files.

User help for other GNOME applications use <desc> tags to
add context for the help file. The additional descriptions
helps the user decide whether or not the topic will help
them to solve their problems.

Also, by not including <desc> tags, gedit's help looked
different than other help guides. This made our docs look
unprofessional, and also hindered findability
(consistently-formatted help helps users to skim the help
more quickly).

This commit adds the <desc> tags to all gedit help files,
making gedit docs more consistent with the rest of GNOME
user help.

docs: See prior commit. Update to include desc tags.

Prior commit just removed one duplicate help file.
Left-out the git-add step. This commit rectifies this.

docs: All pages have <desc> tags w/a closing period.

Updated all help files to make sure they include a desc
tag and included a period at the end of each
description.