Update Sanic adapter unit tests to be compatible with the latest version

[seratch]

The latest version of Sanic web framework verifies if Sanic app names are duplicated in the same Python process.

$ pip install -U sanic
Installing collected packages: sanic
  Attempting uninstall: sanic
    Found existing installation: sanic 20.9.1
    Uninstalling sanic-20.9.1:
      Successfully uninstalled sanic-20.9.1
Successfully installed sanic-20.12.0

$ ./scripts/run_tests.sh tests/adapter_tests_async/test_async_sanic.py

tests/adapter_tests_async/test_async_sanic.py .FFF                                                                                             [100%]
====================================================================== FAILURES ======================================================================
______________________________________________________________ TestSanic.test_shortcuts ______________________________________________________________

self = <tests.adapter_tests_async.test_async_sanic.TestSanic object at 0x10a2c6c10>

    @pytest.mark.asyncio
    async def test_shortcuts(self):
        app = AsyncApp(
            client=self.web_client,
            signing_secret=self.signing_secret,
        )

        async def shortcut_handler(ack):
            await ack()

        app.shortcut("test-shortcut")(shortcut_handler)

        input = {
            "type": "shortcut",
            "token": "verification_token",
            "action_ts": "111.111",
            "team": {
                "id": "T111",
                "domain": "workspace-domain",
                "enterprise_id": "E111",
                "enterprise_name": "Org Name",
            },
            "user": {"id": "W111", "username": "primary-owner", "team_id": "T111"},
            "callback_id": "test-shortcut",
            "trigger_id": "111.111.xxxxxx",
        }

        timestamp, body = str(int(time())), f"payload={quote(json.dumps(input))}"

>       api = Sanic(name="awesome-slack-app")

tests/adapter_tests_async/test_async_sanic.py:140:

Category (place an x in each of the [ ])

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others (tests)

Requirements (place an x in each [ ])

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.

[codecov]

Codecov Report

Merging #187 (7066683) into main (4660bbc) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #187   +/-   ##
=======================================
  Coverage   91.77%   91.77%           
=======================================
  Files         149      149           
  Lines        4448     4448           
=======================================
  Hits         4082     4082           
  Misses        366      366           

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