Bump default theme versions for WordPress 6.7

[mukesh27]

All bundled themes from 2010 to 2024 will need a version bump for the 6.7 release.

Previously:
#60701 - 6.6
#59816 - 6.5
#58832 - 6.4
#57857 - 6.3
#57689 - 6.2
#56450 - 6.1
#55754 - 6.0
#54783 - 5.9
#53277 - 5.8
#52704 - 5.7
#51919 - 5.6
#50889 - 5.5
#49743 - 5.4