fix: setting child concurrency during headless install (#3405)

close #3399

.changeset/fluffy-goats-double.md

@@ -0,0 +1,5 @@
+---
+"supi": patch
+---
+
+Pass `childConcurrency` option to `@pnpm/headless`. Setting `childConcurrency` should have an effect during frozen lockfile installation.

packages/supi/src/install/index.ts

@@ -226,6 +226,7 @@ export async function mutateModules (
         }
         try {
           await headless({
+            childConcurrency: opts.childConcurrency,
             currentEngine: {
               nodeVersion: opts.nodeVersion,
               pnpmVersion: opts.packageManager.name === 'pnpm' ? opts.packageManager.version : '',