pgadmin: use new yarn-berry_3 fetcher

[gador]

Uses new yarn fetcher. See #399404

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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[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review/3032/5431

[yuyuyureka]

Would be nice if you added me to the co-authors. Or rather, if you're copying most of the contents from one of my commits, cherry-pick and amend to it.

[gador]

Would be nice if you added me to the co-authors. Or rather, if you're copying most of the contents from one of my commits, cherry-pick and amend to it.

Sure! Since I had to do some modifications, I just added you as Co-author instead of cherry-picking

[SuperSandro2000]

nixpkgs-review result

Generated using nixpkgs-review.

Command: nixpkgs-review pr 402519

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x86_64-linux

✅ 4 packages built:

• pgadmin4
• pgadmin4-desktopmode
• pgadmin4-desktopmode.dist
• pgadmin4.dist