fix(django): Set active thread ID when middleware spans are disabled

[alexander-alderman-webb]

Description

Set the active thread ID on Django server transactions independently of the middleware_spans option.

The test_active_thread_id() test previously failed if middleware spans are disabled.

Issues

Contributes to #5062

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:)
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