pinact: exclude bin/gen-jsonschema

Which was introduced in version 1.1.2
However it looks like a project internal tool

For example, homebrew did not include it
https://github.com/Homebrew/homebrew-core/blob/2e88df3e7a7a39f4d0cd462a0f46d73861d7af8d/Formula/p/pinact.rb#L20-L28

Author: kachick

pkgs/by-name/pi/pinact/package.nix

@@ -43,6 +43,10 @@ buildGoModule {
     "-X main.version=${version} -X main.commit=v${version}"
   ];
 
+  subPackages = [
+    "cmd/pinact"
+  ];
+
   meta = {
     inherit mainProgram;
     description = "Pin GitHub Actions versions";