[False-Positive]: Vyper constant-states

### Describe the false alarm that Slither raises and how you know it's inaccurate:

Slither can report that a non-constant state variable that is being updated should be constant.

Additionally, there seems to be some non-determinism involved as it is not reported every time (running Slither multiple times without changing the file can yield a different amount of results each time)
See in the log output two consecutive run results.

[EDIT] the issue seems to be fixed on the `dev` branch
### Frequency

Very Frequently

### Code example to reproduce the issue:

```Vyper
# @version 0.3.7

x: public(uint256)

@external
def foo():
x:uint256 = 12
x += 1
self.x = x
```

### Version:

`0.10.1`

### Relevant log output:

```shell
~/shared/ slither contracts/lending/Foo.vy
INFO:Detectors:
Foo.foo().x (contracts/lending/Foo.vy#7) shadows:
- Foo.x (contracts/lending/Foo.vy#3) (state variable)
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#local-variable-shadowing
INFO:Detectors:
Foo.x (contracts/lending/Foo.vy#3) should be constant
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#state-variables-that-could-be-declared-constant
INFO:Slither:contracts/lending/Foo.vy analyzed (1 contracts with 94 detectors), 2 result(s) found

~/shared/ slither contracts/lending/Foo.vy
INFO:Detectors:
Foo.foo().x (contracts/lending/Foo.vy#7) shadows:
- Foo.x (contracts/lending/Foo.vy#3) (state variable)
Reference: https://github.com/crytic/slither/wiki/Detector-Documentation#local-variable-shadowing
INFO:Slither:contracts/lending/Foo.vy analyzed (1 contracts with 94 detectors), 1 result(s) found
```

Run Slither 0.10.1 repeatedly against the Vyper example in the issue and compare the detector output between runs. Review the dev branch, where the reporter says the issue is fixed; done means the updated state variable is not falsely reported as constant and repeated runs are consistent.

Written by the indexing model from the issue text.