ref(transport): Remove redundant checks for dsn (#6104)

### Description
#### Related Issue
* Fixes #6089

#### What changed
Removed the redundant `is not None` check from the DSN conditional
statement in `Transport.init` (`transport.py`).

**Code Comparison:**
```python
# Before
if options and options["dsn"] is not None and options["dsn"]:

# After
if options and options["dsn"]:
```

####  Why
In Python, the truthiness check (`options["dsn"]`) inherently evaluates
`None` as falsy. Therefore, the explicit `is not None` guard is
redundant. Removing it simplifies the logic while maintaining the same
behavior.

####  Notes
* **Why not use `options.get('dsn')`?** While `.get()` is often used for
safe dictionary access, a default value for `"dsn"` is already
guaranteed in this context, so there is no risk of a `KeyError`.
* **Consistency:** I intentionally kept the direct dictionary access
(`options["dsn"]`) to remain consistent with the existing coding pattern
used later in the same file (e.g., line 1165: `if options["dsn"]:`).

Author: psh9508

sentry_sdk/transport.py

@@ -106,7 +106,7 @@ class Transport(ABC):
 
     def __init__(self: "Self", options: "Optional[Dict[str, Any]]" = None) -> None:
         self.options = options
-        if options and options["dsn"] is not None and options["dsn"]:
+        if options and options["dsn"]:
             self.parsed_dsn = Dsn(options["dsn"], options.get("org_id"))
         else:
             self.parsed_dsn = None