Broken AMINO with `x/tx v0.13.6`

[fmorency]

CosmosSDK x/tx >= v0.13.6 broke the AMINO signing of MsgRemovePending & MsgCreateValidator.

It works well with <= v0.13.5.

The impact of this issue is limited.

Run with v0.13.5: https://github.com/liftedinit/manifestjs/actions/runs/13632313075/job/38102620733
Run with v0.13.6:

• Broken MsgRemovePending: https://github.com/liftedinit/manifestjs/actions/runs/13633297618/job/38105806392
• Broken MsgCreateValidator: https://github.com/liftedinit/manifestjs/actions/runs/13633081350/job/38105111298