chore: Drop 3.6 from CI

[sentrivana]

Description

Remove 3.6 from CI and CI templates on the new major branch.

Issues

Closes #4999

Reminders

• Please add tests to validate your changes, and lint your code using tox -e linters.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
24368	1	24367	1706

View the top 1 failed test(s) by shortest run time

tests.integrations.sanic.test_sanic::test_bad_request_not_captured

Stack Traces | 0.143s run time

.../integrations/sanic/test_sanic.py:181: in test_bad_request_not_captured
    with c as client:
.tox/py3.9-sanic-v25.3.0/lib/python3.9........./site-packages/sanic_testing/reusable.py:65: in __enter__
    self.run()
.tox/py3.9-sanic-v25.3.0/lib/python3.9........./site-packages/sanic_testing/reusable.py:77: in run
    self._server = self._run(self._server_co)
.tox/py3.9-sanic-v25.3.0/lib/python3.9........./site-packages/sanic_testing/reusable.py:198: in _run
    return self._loop.run_until_complete(coro)
.../hostedtoolcache/Python/3.9.24....../x64/lib/python3.9/asyncio/base_events.py:647: in run_until_complete
    return future.result()
.tox/py3.9-sanic-v25.3.0/lib/python3.9.../sanic/mixins/startup.py:604: in create_server
    return await serve(
.tox/py3.9-sanic-v25.3.0/lib/python3.9.../sanic/server/async_server.py:113: in __await__
    self.server = task.result()
.../hostedtoolcache/Python/3.9.24....../x64/lib/python3.9/asyncio/base_events.py:1506: in create_server
    raise OSError(err.errno, 'error while attempting '
E   OSError: [Errno 98] error while attempting to bind on address ('127.0.0.1', 8084): address already in use

To view more test analytics, go to the Test Analytics Dashboard
_{📋 Got 3 mins? Take this short survey to help us improve Test Analytics.}