Update version to 0.930+dev (#11770)

This is for the 0.930 release branch. I'll update the master to
0.940+dev afterwards.

Author: JukkaL

Diff for: mypy/version.py

@@ -5,7 +5,7 @@
 # - Release versions have the form "0.NNN".
 # - Dev versions have the form "0.NNN+dev" (PLUS sign to conform to PEP 440).
 # - For 1.0 we'll switch back to 1.2.3 form.
-__version__ = '0.920+dev'
+__version__ = '0.930+dev'
 base_version = __version__
 
 mypy_dir = os.path.abspath(os.path.dirname(os.path.dirname(__file__)))