Discard protodep

[youngjoon-lee]

The CI began to throw an error: https://github.com/medibloc/panacea-core/runs/3170573276

protodep up --use-https
[INFO] force update = false
[INFO] cleanup cache = false
[INFO] identity file = 
[INFO] use https = true
[INFO] Getting github.com/cosmos/cosmos-sdk 
[INFO] 84c33215658131d87daf3c629e909e12ed9370fa is not a tag, checking out by hash
[INFO] Getting github.com/cosmos/cosmos-sdk 
[INFO] 84c33215658131d87daf3c629e909e12ed9370fa is not a tag, checking out by hash
Error: checkout to 84c33215658131d87daf3c629e909e12ed9370fa is failed: worktree contains unstaged changes

I've checked the cosmos/cosmo-sdk git repo, but I couldn't find any issue. The commit 84c33215658131d87daf3c629e909e12ed9370fa exists in that git repo.

I suspect that something was broken in the protodep. So, let's remove the protodep. We can probably use buf instead of protodep, but not that urgent.

[youngjoon-lee]

Or, we can refer to https://github.com/cosmos/cosmos-sdk/blob/84c33215658131d87daf3c629e909e12ed9370fa/Makefile#L421