**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
if extra.get('shared_access_key') or extra.get('extra__wasb__shared_access_key'):
            shared_access_key = extra.get('shared_access_key') or extra.get('extra__wasb__shared_access_key')
            
            return BlobServiceClient(account_url=conn.host, credential=shared_access_key)
        if extra.get('tenant_id') or extra.get('extra__wasb__tenant_id'):
            
            app_id = conn.login
            app_secret = conn.password
            tenant = extra.get('tenant_id') or extra.get('extra__wasb__tenant_id')
            token_credential = ClientSecretCredential(tenant, app_id, app_secret)
            return BlobServiceClient(account_url=conn.host, credential=token_credential)
        sas_token = extra.get('sas_token') or extra.get('extra__wasb__sas_token')
        if sas_token and sas_token.startswith('https'):
            return BlobServiceClient(account_url=extra.get('sas_token'))
        if sas_token and not sas_token.startswith('https'):
            return BlobServiceClient(account_url=f"https://{conn.login}.blob.core.windows.net/" + sas_token)
        else:
            
            return BlobServiceClient(
                account_url=f"https://{conn.login}.blob.core.windows.net/", credential=conn.password, **extra
            )
    def _get_container_client(self, container_name: str) -> ContainerClient:
        """
        Instantiates a container client
        :param container_name: The name of the container
        :type container_name: str
        :return: ContainerClient
        """
        return self.connection.get_container_client(container_name)
    def _get_blob_client(self, container_name: str, blob_name: str) -> BlobClient: