upgrade to go 1.19 for v8

[faddat]

Go versions can't be too low, but they can be too high.

For greater consistency, we can upgrade to go 1.19 so that all validators will be using the same go runtime.

• 1 validator set should use 1 major release of golang cosmos-sdk#13976

[mpoke]

Thanks @faddat for opening the issue. Gaia v8 and v9 will use SDK 0.45.11, which uses go 1.18. Once we update to SDK 0.47, we'll also upgrade the go version.