Since Go v1.21 was released, in order to keep up with their maintained releases, we should bump the minimum Go version on a few of our release branches:

Remember to inform SDK and other users prior to bumping Go versions.

• chore: Bump minimum Go version on main to v1.21 #1244
• Bump the minimum Go version for v0.38 to Go v1.21
• Bump the minimum Go version for v0.34 to Go v1.20 (since v1.19 is no longer maintained)