Make 16.3/7.3 minimum required version to upgrade to 16.4/7.4

Summary

As 16.3 is a confirmed scheduled upgrade stop, marking it as a stop before upgrading any further.

Acceptance criteria

• Attempt to upgrade from any version prior to 16.3/7.3 -> 16.4/7.4 will be prevented and output a suggestion to upgrade to 16.3/7.3 first

Previous examples:

• Make 15.11/6.11 minimum required version to upg... (#4522 - closed)
• Only permit 15.0 upgrade from 14.10 - !2562 (merged)
• Only permit upgrades from 4.12 - !2029 (merged)