common.py: update ArgumentParser to 1.2.0 (swiftlang#737)

* common.py: update ArgumentParser to 1.1.4

This version bump would benefit SwiftPM, Swift Driver, and SourceKit-LSP, which all use ArgumentParser.

* common.py: update ArgumentParser to 1.2.0

Author: MaxDesiatov

common.py

@@ -36,7 +36,7 @@
         'swift-corelibs-libdispatch': 'main',
         'swift-corelibs-foundation': 'main',
         'swift-corelibs-xctest': 'main',
-        'swift-argument-parser': '1.0.3',
+        'swift-argument-parser': '1.2.0',
         'swift-driver': 'main',
         'yams': '4.0.2',
         'swift-tools-support-core': 'main',