non-free.md: remove FusionInvoice

See discussion in #1437

> https://invoiceplane.com/ - https://github.com/InvoicePlane/InvoicePlane is already listed in the main list and is FOSS. It was open sourced by https://www.fusioninvoice.com/ (v1) when their v2 came out. - FusionInvoice (v2) (proprietary) is shutting down and their product is now available as Free Software in
https://github.com/InvoicePlane/InvoicePlane/tree/2.0, but not marked stable yet.

non-free.md

@@ -60,7 +60,6 @@
 ## Money, Budgeting and Management
 
   * [Anchor](http://theanchorapp.com/) - Anchor is an invoicing system that integrates with Stripe and Paypal. Includes features such as: reporting, dashboard and no client limit. ([Demo](http://theanchorapp.com/demo/admin-login)) `PHP`
-  * [FusionInvoice](https://www.fusioninvoice.com) `⊘ Proprietary` - FusionInvoice is an invoicing system for freelancers and small businesses. `PHP`
   * [Manager](http://manager.io/server) `⊘ Proprietary` - Online accounting software for small businesses. `Mono`
   * [Pancake](http://pancakeapp.com/) `⊘ Proprietary` - Online invoicing, project management, time tracking and proposal software. `PHP`