Update CONTRIBUTING.MD

Author: ibrahimoktay

CONTRIBUTING.md

@@ -10,6 +10,7 @@ To build the `main` branch of SwiftSyntax, follow the following instructions:
     ```
     - (enclosing directory)
       - swift
+      - swift-argument-parser
       - swift-syntax
     ```
 
@@ -30,8 +31,6 @@ To build the `main` branch of SwiftSyntax, follow the following instructions:
 
 Swift-CI will automatically run the code generation step whenever a new toolchain (development snapshot or release) is published. It should thus almost never be necessary to perform the above build yourself.
 
-Afterward, SwiftPM can also generate an Xcode project to develop SwiftSyntax by running `swift package generate-xcodeproj`.
-
 If you also want to run tests locally, read the section below as testing has additional requirements.
 
 ## Local Testing