ref(tracing): Disable Django middleware span auto-instrumentation

[JoshFerge]

It has been very rare that we've needed to debug the performance of our middleware spans, and these are a significant volume of our span telemetry we send. Let's disable them and re-add telemetry in specific places if needed.

We'll also still have profiles which can be used to debug these middlewares with full detail, if needed.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
29574	1	29573	146

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

tests.sentry.deletions.test_group.DeleteIssuePlatformTest::test_simple_issue_platform

Stack Traces | 6.33s run time

#x1B[1m#x1B[.../sentry/deletions/test_group.py#x1B[0m:439: in test_simple_issue_platform
    assert self.select_issue_platform_events(self.project.id) is None
#x1B[1m#x1B[31mE   AssertionError: assert {'event_id': 'd51c575f89cf4db09f011004f084fc92', 'group_id': 31, 'occurrence_id': 'b1bb22ac70c84b8cbcfb635d3d5929a9'} is None#x1B[0m
#x1B[1m#x1B[31mE    +  where {'event_id': 'd51c575f89cf4db09f011004f084fc92', 'group_id': 31, 'occurrence_id': 'b1bb22ac70c84b8cbcfb635d3d5929a9'} = <bound method DeleteIssuePlatformTest.select_issue_platform_events of <tests.sentry.deletions.test_group.DeleteIssuePlatformTest testMethod=test_simple_issue_platform>>(4557023143788546)#x1B[0m
#x1B[1m#x1B[31mE    +    where <bound method DeleteIssuePlatformTest.select_issue_platform_events of <tests.sentry.deletions.test_group.DeleteIssuePlatformTest testMethod=test_simple_issue_platform>> = <tests.sentry.deletions.test_group.DeleteIssuePlatformTest testMethod=test_simple_issue_platform>.select_issue_platform_events#x1B[0m
#x1B[1m#x1B[31mE    +    and   4557023143788546 = <Project at 0x7fe5b5a7c2c0: id=4557023143788546, team_id=None, name='Bar', slug='bar', organization_id=4557023143788544>.id#x1B[0m
#x1B[1m#x1B[31mE    +      where <Project at 0x7fe5b5a7c2c0: id=4557023143788546, team_id=None, name='Bar', slug='bar', organization_id=4557023143788544> = <tests.sentry.deletions.test_group.DeleteIssuePlatformTest testMethod=test_simple_issue_platform>.project#x1B[0m

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