False positive redundant-condition on use of nonlocal

### Describe the Bug

The following program with pyrefly 1.1.0 and `--min-severity=warn` gives the error:

` WARN String literal used as condition. It's equivalent to 'False' [redundant-condition]`

However, actually running the program shows that the condition is definitely not false.

I'm guessing the use of `nonlocal` is confusing pyrefly.

```
def bug():
dynamic = ''

def changedynamic():
nonlocal dynamic
dynamic = 'not empty'

changedynamic()
if dynamic:
print('If equivalent to false, then why are you seeing this?')

bug()
```

### Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeSImMYABNgK4DmAFAJSIA66NPNmp6VAFsIAYxoBeGgHJpXLrz7UaogBYZGMfoJGi2nbot7pc6KLlGoofAcLEKjPbXfFTpJgC40YQ4h9Jy6A48ahpatrpswTQQtM66Bo48xABOEOgezNIAkrQwAI70EABuVjAZNB64NGBWcDAANJWq5TQA7qqkNKgpMDSkuPQ09TDpjM0QcAD80qzy6Awsc%2BggDSBkvWBQpIRVQlAUAMQ0AAqkm9vDGDgEKqaQjPQpqB4QpoRcxwDKMH2qHh5iHBEAB6EEbajbQi4FKMEHlEGYCxwEGie4QR7PV6mEE1GHdUrQVDYWB3dAPJ4vN7cXB%2BalwD7oMgeVSmAC0xRgKTg1MkNA4IAAzIQAIwAJgFXAA2lyUjC4ABdLj0dAQXwwjxaNmYCC9USvTl86QYky9QKeNm9Qq6rUAaxgpDZqFEongcCNbR66ECIAAvmtnQaYAAxaAwChoLB4IhkP1AA

### (Only applicable for extension issues) IDE Information

_No response_

Reproduce the warning with the linked sandbox or the provided Python program using pyrefly 1.1.0 and --min-severity=warn. Trace how the redundant-condition check handles the nonlocal assignment; done means the condition is no longer reported as equivalent to False while other redundant-condition diagnostics remain correct.

Written by the indexing model from the issue text.