fix: remove duplicated message type events

[dadamu]

Description

Currently, the sdk.MessageEventType is emitted twice in Desmos, it is because that cosmos-sdk already handles the default message type event.
As we can see, the example transaction has two message type event:

[
    {
        "events": [
            {
                "type": "message",
                "attributes": [
                    {
                        "key": "action",
                        "value": "/desmos.posts.v3.MsgCreatePost"
                    },
                    {
                        "key": "sender",
                        "value": "desmos1q35n50xnlj7lapfkzzcq5rvypcvhure0rr945u"
                    }
                ]
            },
            {
                "type": "message",
                "attributes": [
                    {
                        "key": "module",
                        "value": "posts"
                    },
                    {
                        "key": "action",
                        "value": "/desmos.posts.v3.MsgCreatePost"
                    },
                    {
                        "key": "sender",
                        "value": "desmos1q35n50xnlj7lapfkzzcq5rvypcvhure0rr945u"
                    }
                ]
            },
         ...skip
]

To fix it, we can safely remove the sdk.MessageEventType event inside Desmos modules.
References:
https://docs.cosmos.network/v0.47/learn/advanced/events#default-events
https://github.com/cosmos/cosmos-sdk/blob/v0.47.5/baseapp/baseapp.go#L848

---

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (cfefad2) 81.46% compared to head (22ed971) 81.04%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1284      +/-   ##
==========================================
- Coverage   81.46%   81.04%   -0.43%     
==========================================
  Files         218      218              
  Lines       18287    17880     -407     
==========================================
- Hits        14897    14490     -407     
  Misses       2778     2778              
  Partials      612      612              

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[RiccardoM]

Thank you Paul! 🙏