[`flake8-comprehensions`] Fix `C420` to prepend whitespace when needed (#18616)
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## Summary
This PR fixes rule C420's fix. The fix replaces `{...}` with
`dict....(...)`. Therefore, if there is any identifier or such right
before the fix, the fix will fuse that previous token with `dict...`.
The example in the issue is
```python
0 or{x: None for x in "x"}
# gets "fixed" to
0 ordict.fromkeys(iterable)
```
## Related Issues
Fixes: https://github.com/astral-sh/ruff/issues/18599
ruff
34052a11 - [`flake8-comprehensions`] Fix `C420` to prepend whitespace when needed (#18616)
