Update SynfigStudio v1.4 file format support

Summary:

SynfigStudio new stable version v1.4.0 has been released. It's time to support the new file format used by that version

Steps to reproduce:

  • open Inkscape
  • draw any shape using bline tool
  • save it with Synfig Animation(*.sif) format

What happened?

Outdated version dialog was presented. See attachment below

What should have happened?

Inkscape should support the new file format so that warning dialog won't be triggered for the said animation program

Sample attachments:

Screenshot_from_2020-11-15_07-56-43

Version Info:

- Inkscape Version: Inkscape 1.0.1 (3bc2e813f5, 2020-09-07)
- Operating System: Debian
- Operating System version: Unstable