Update exos.gns3a

[stewilliams-extr]

Added EXOS 32.6.3.126. All older versions will need to be removed. Future releases can and will be added.

Before submitting a pull request, please check the following.

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When updating an existing appliance:

• [x ] The new version is on top.
• [x ] The filenames in the "images" section are unique, to avoid appliances / version overwriting each other.
• [x ] If you forked the repo, running check.py doesn't drop any errors for the updated file.

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When creating a new appliance:

• It's tested locally, i.e.
  • [x ] You dragged an instance into a project on your box, got it installed (if necessary), and did some basic network checks (ping, UI reachable, etc.).
  • [x ] GNS3 VM can run it without any tweaks.
  • [x ] The device is in the right category: router, switch, guest (hosts), firewall
  • [ x] You filled in as much info as possible (checks the schemas and other appliance files for some guidance).
• When adding a container: it builds on Docker Hub and can be pulled.
• [ x] The filenames in the "images" section are unique (to avoid appliances and/or versions overwriting each other).
• [ x] If you forked the repo, running check.py doesn't drop any errors for the new file.
• Optional: a symbol has been created for the new appliance.