nixos/lib/test-driver: Revert magick args order

[OPNA2608]

...as it apparently matters when we do the -negate

#375504 changed where the -negate in the list of magick commands for OCR pre-processing happens. This gets most OCR commands in nixosTests.lomiri* tests stuck (i.e. the user name on the lightdm lomiri greeter in nixosTests.lomiri.greeter, "Rotation Lock" in the lomiri settings app in nixosTests.lomiri.{desktop-basics,desktop-appinteractions}).

machine: waiting for (AM|PM) to appear on screen
machine # [   43.596169] systemd[1]: systemd-timedated.service: Deactivated successfully.
machine # [   47.628680] systemd[1]: systemd-hostnamed.service: Deactivated successfully.
(finished: waiting for (AM|PM) to appear on screen, in 20.34 seconds)
machine: making screenshot /nix/store/b30ywc00v4bvhxn8jqazi8029vrxyyan-vm-test-run-lomiri-greeter/lomiri_greeter_launched.png
(finished: making screenshot /nix/store/b30ywc00v4bvhxn8jqazi8029vrxyyan-vm-test-run-lomiri-greeter/lomiri_greeter_launched.png, in 0.29 seconds)
machine: sending key 'ret'
(finished: sending key 'ret', in 0.01 seconds)
machine: must succeed: sleep 10
(finished: must succeed: sleep 10, in 10.05 seconds)
machine: waiting for Alice Foobar to appear on screen
machine # [  907.191483] systemd[1]: Starting Cleanup of Temporary Directories...
machine # [  907.341173] systemd[1]: systemd-tmpfiles-clean.service: Deactivated successfully.
machine # [  907.343061] systemd[1]: Finished Cleanup of Temporary Directories.
timeout reached; test terminating...

With the assumption that this was done for convenience instead of fixing any OCR issue in another setup, restore the original order of magick args.

With #375365 applied to fix all required test dependencies, all of nixosTests.lomiri passes again.

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/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 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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