Merge pull request #4821 from wordpress-mobile/try/fix-pnpm-version

Fix pnpm version issue

package.json

@@ -53,7 +53,7 @@
 		"wd": "^1.11.1"
 	},
 	"scripts": {
-		"postinstall": "patch-package && npm ci --prefix gutenberg && npm run i18n:check-cache && cd jetpack/projects/plugins/jetpack && npx pnpm install",
+		"postinstall": "patch-package && npm ci --prefix gutenberg && npm run i18n:check-cache && cd jetpack/projects/plugins/jetpack && npx pnpm@6 install",
 		"start": "echo \"\\x1b[33mThe start command is not available in this project. It is strongly recommended to use \\x1b[1:33mstart:reset\\x1b[0m\\x1b[33m to perform some cleanup when starting the metro bundler.\nOr you may use \\x1b[1:33mstart:quick\\x1b[0m\\x1b[33m for a quicker startup, but this may lead to unexpected javascript errors when running the app.\\x1b[0m\"",
 		"start:reset": "npm run core clean:runtime && npm run start:quick -- --reset-cache",
 		"start:quick": "react-native start --config ./metro.config.js",