**Apache Airflow version**: 2.0.1

**Environment**:

- **Cloud provider or hardware configuration**: docker container
- **OS** (e.g. from /etc/os-release): `Debian GNU/Linux 10 (buster)`
- **Kernel** (e.g. `uname -a`): `Linux 69a18af222ff 3.10.0-1160.15.2.el7.x86_64 #1 SMP Thu Jan 21 16:15:07 EST 2021 x86_64 GNU/Linux`
- **Install tools**: `pip`
- **Others**: `azure` extras

**What happened**:

`airflow.providers.microsoft.azure.hooks.wasb.WasbHook.delete_file` unable to delete blobs if both conditions below are true:

* `is_prefix` argument set to `True`
* the target blobs contain at least one '/' character in their names


**What you expected to happen**:
All files starting with the specified prefix are removed.

The problem is caused by this line: https://github.com/apache/airflow/blob/73187871703bce22783a42db3d3cec9045ee1de2/airflow/providers/microsoft/azure/hooks/wasb.py#L410

By not specifying `delimiter = ''` the listed blobs won't be terminal blobs if the target blobs happen to contain the default delimiter (`/`) in their name

**How to reproduce it**:

For example, consider the following scenario. We have a blob container `cnt` with two files:
* `parent/file1`
* `parent/file2`

The following call should delete both files:
``` python
wasb_hook= WasbHook(...)
wasb_hook.delete_file(
    container_name='cnt',
    blob_name='parent',
    is_prefix=True,
)
```
But instead we get an error `Blob(s) not found: ('parent/',)`


airflow/providers/microsoft/azure/hooks/wasb.py
container_name: str,
        blob_name: str,
        is_prefix: bool = False,
        ignore_if_missing: bool = False,
        **kwargs,
    ) -> None:
        """
        Delete a file from Azure Blob Storage.
        :param container_name: Name of the container.
        :type container_name: str
        :param blob_name: Name of the blob.
        :type blob_name: str
        :param is_prefix: If blob_name is a prefix, delete all matching files
        :type is_prefix: bool
        :param ignore_if_missing: if True, then return success even if the
            blob does not exist.
        :type ignore_if_missing: bool
        :param kwargs: Optional keyword arguments that ``ContainerClient.delete_blobs()`` takes.
        :type kwargs: object
        """
        if is_prefix:
            blobs_to_delete = self.get_blobs_list(container_name, prefix=blob_name, **kwargs)
        elif self.check_for_blob(container_name, blob_name):
            blobs_to_delete = [blob_name]
        else:
            blobs_to_delete = []
        if not ignore_if_missing and len(blobs_to_delete) == 0:
            raise AirflowException(f'Blob(s) not found: {blob_name}')
        self.delete_blobs(container_name, *blobs_to_delete, **kwargs)