[BUG] decimal dependency is outdated

**Versions Used**
Kaffy: 0.11.0
Phoenix: 1.8.4
Elixir: 1.20.1
MyXQL: 0.9.0

**What's actually happening?**
Actual version of decimal is 3.1.1
Kaffy depends on 2.2 version
Installation fails.

**What should happen instead?**
White rabbits falling from the heaven?

**Screenshots**
```
Because kaffy >= 0.10.3 depends on decimal ~> 2.2 and myxql >= 0.9.0 depends on decimal ~> 3.0, kaffy >= 0.10.3 is incompatible with myxql >= 0.9.0.
And because your app depends on kaffy ~> 0.11.0, myxql >= 0.9.0 is forbidden.
So, because your app depends on myxql ~> 0.9, version solving failed.
```