Remove python-appindicator and gir1.2-appindicator-0.1

gir1.2-appindicator-0.1 has no reverse dependencies (it is for gtk2 GObject Introspection)

There are only 2 packages that recommend python-appindicator. It would be trivial to drop the recommends. Those 2 packages (deluge and
gtk-recordmydesktop) will probably be removed from Debian approx. September 2019 because they use pygtk.

$ reverse-depends python-appindicator
Reverse-Recommends
==================
* deluge-gtk
* gtk-recordmydesktop

previous reverse depends
-----------------------
* cherrytree — dependency on python-appindicator was dropped early in bionic. RM requested in LP: #1731725
* hamster-indicator - source package was removed (LP: #1739797)

--------------------------
OTHER GTK2 REVERSE DEPENDS
--------------------------
The other gtk2 libraries for libappindicator aren't planned for removal yet.

$ reverse-depends libappindicator0.1-cil
Reverse-Depends
===============
* libappindicator0.1-cil-dev
* tasque

$ reverse-depends libappindicator1
Reverse-Recommends
==================
* nautilus-dropbox

Reverse-Depends
===============
* alarm-clock-applet
* gir1.2-appindicator-0.1 (proposed removal here)
* gmpc
* growl-for-linux
* gxkb
* hime
* indicator-application-gtk2
* libappindicator-dev
* libappindicator0.1-cil
* nitroshare
* parcellite
* python-appindicator (proposed removal here)
* quicksynergy
* wallch