dd-trace-py fix(wsgi): do not mark StopIteration spans with error

Following this: https://github.com/miguelgrinberg/flask-sock/issues/64#issuecomment-1664709789 StopIteration is just a normal expected exception upon socket close. I am wondering if we should re-raise though? If we do, then we need to add additional code so this isn't marked as an error.

Checklist

[x] Change(s) are motivated and described in the PR description
[x] Testing strategy is described if automated tests are not included in the PR
[x] Risks are described (performance impact, potential for breakage, maintainability)
[x] Change is maintainable (easy to change, telemetry, documentation)
[x] Library release note guidelines are followed or label changelog/no-changelog is set
[x] Documentation is included (in-code, generated user docs, public corp docs)
[x] Backport labels are set (if applicable)
[x] If this PR changes the public interface, I've notified @DataDog/apm-tees.
[x] If change touches code that signs or publishes builds or packages, or handles credentials of any kind, I've requested a review from @DataDog/security-design-and-guidance.

Reviewer Checklist

[x] Title is accurate
[x] All changes are related to the pull request's stated goal
[x] Description motivates each change
[x] Avoids breaking API changes
[x] Testing strategy adequately addresses listed risks
[x] Change is maintainable (easy to change, telemetry, documentation)
[x] Release note makes sense to a user of the library
[x] Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
[x] Backport labels are set in a manner that is consistent with the release branch maintenance policy

Jan 19 '24 19:01 ZStriker19

Benchmarks

Benchmark execution time: 2024-01-31 19:12:28

Comparing candidate commit 609f3453ff1a2ba9153d76e34d9998e60f195640 in PR branch zachg/ignore_stopiteration_exception with baseline commit 222ce130c5bdbfbafc92de1a88361e164b8dae19 in branch main.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 194 metrics, 9 unstable metrics.