update version

Author: Jintao-Huang

swift/version.py

@@ -1,5 +1,5 @@
 # Make sure to modify __release_datetime__ to release time when making official release.
-__version__ = '1.6.0'
+__version__ = '1.6.1'
 # default release datetime for branches under active development is set
 # to be a time far-far-away-into-the-future
 __release_datetime__ = '2099-10-13 08:56:12'