### What problem does this PR solve?
The removed if statement is unnecessary and adds cognitive load for
readers.
The original code:
```
vector_similarity_weight = req.get("vector_similarity_weight", 0.3)
if vector_similarity_weight is None:
vector_similarity_weight = 0.3
```
has been simplified to:
```
vector_similarity_weight = req.get("vector_similarity_weight", 0.3)
```
### Type of change
- [x] Refactoring
44ac87aef4