maintainers: remove martfont

[SuperSamus]

Description of changes

I didn't do much here, especially compared to others who left, and technically I'm not directly affected by all that's happening behind the scenes. But what happened is a clown show. After this new definition of "permanent ban," I wonder what new exciting definitions are there going to be in the future.
Even ignoring all that, with many maintainers gone... what am I doing here?

Depends on #320861, since that removes a package where I'm listed as maintainer.

Do whatever you want with my remaining PRs.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[wegank]

Rebased as #320861 is merged.