Standardize test usage of context: Context across operator tests (avoid context=None)

### Description

### Title

Standardize test usage of `context: Context` across operator tests (avoid `context=None`)

---

### Description

Many operator tests across the Airflow codebase currently invoke `execute()` like this:
related:

https://github.com/apache/airflow/blob/main/providers/microsoft/azure/src/airflow/providers/microsoft/azure/operators/wasb_delete_blob.py

https://github.com/apache/airflow/blob/main/providers/microsoft/azure/tests/unit/microsoft/azure/operators/test_wasb_delete_blob.py

test code

```python
operator.execute(None)
```

However, the `execute()` method is explicitly typed as:

```python
def execute(self, context: Context) -> None:
```

To align with this contract and improve typing correctness and future maintainability, we should replace `None` with a minimal `Context` object (e.g., `{}` or `MagicMock(spec=Context)`).

#### Benefits of this change:
- Aligns test cases with actual method signature (`context: Context`)
- Avoids potential mypy/type-checking issues (especially in Airflow 3+)
- Prevents misleading behavior in tests by not passing `None` when `context` is required
- Improves clarity and correctness in test expectations

---

### Suggested Migration Pattern

**Before:**
```python
operator.execute(None)
```

**After:**
```python

if TYPE_CHECKING:
try:
from airflow.sdk.definitions.context import Context
except ImportError:
# TODO: Remove once provider drops support for Airflow 2
from airflow.utils.context import Context

mock_context: Context = {}
operator.execute(mock_context)
```

**Or (stricter typing):**
```python
from unittest.mock import MagicMock

if TYPE_CHECKING:
try:
from airflow.sdk.definitions.context import Context
except ImportError:
# TODO: Remove once provider drops support for Airflow 2
from airflow.utils.context import Context

mock_context = MagicMock(spec=Context)
operator.execute(mock_context)
```

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

Start with providers/microsoft/azure/tests/unit/microsoft/azure/operators/test_wasb_delete_blob.py and the related wasb_delete_blob.py operator. Inspect how the tests call execute(None), then use the proposed Context-based pattern consistently across the operator tests. Run the referenced test file and confirm the tests pass without passing None to execute().

Written by the indexing model from the issue text.