Bump version number on main branch (which is now targeting the 7.0 re…

…lease) (#1704)

This PR updates the version number on the main branch; the main branch is now targeting the 7.0 release.

There's a maint/6.4 branch targeting the upcoming 6.4 release.

setup.py

@@ -18,8 +18,8 @@
 # release. The actual package version is autogenerated from this information
 # together with information from the version control system, and then injected
 # into the package source.
-MAJOR = 6
-MINOR = 4
+MAJOR = 7
+MINOR = 0
 MICRO = 0
 PRERELEASE = ""
 IS_RELEASED = False