Fix span status for 4XX responses

[alecsammon]

For servers then Span Status should only be set to Error for responses >= 500, and 400 should be left unset.

See https://github.com/open-telemetry/semantic-conventions/blob/main/docs/http/http-spans.md?plain=1#L108-L112

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.80%. Comparing base (15427f3) to head (86fa1de).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #290   +/-   ##
=========================================
  Coverage     84.80%   84.80%           
  Complexity      947      947           
=========================================
  Files            80       80           
  Lines          3798     3798           
=========================================
  Hits           3221     3221           
  Misses          577      577           

Flag	Coverage Δ
Aws	85.75% <ø> (ø)
Context/Swoole	0.00% <ø> (ø)
Instrumentation/CodeIgniter	73.94% <ø> (ø)
Instrumentation/ExtAmqp	89.58% <ø> (ø)
Instrumentation/Guzzle	69.73% <ø> (ø)
Instrumentation/HttpAsyncClient	81.33% <ø> (ø)
Instrumentation/IO	70.90% <ø> (ø)
Instrumentation/MongoDB	77.33% <ø> (ø)
Instrumentation/OpenAIPHP	86.82% <ø> (ø)
Instrumentation/PDO	89.56% <ø> (ø)
Instrumentation/Psr14	78.12% <ø> (ø)
Instrumentation/Psr15	93.50% <ø> (ø)
Instrumentation/Psr16	97.50% <ø> (ø)
Instrumentation/Psr18	82.08% <ø> (ø)
Instrumentation/Psr3	61.03% <ø> (ø)
Instrumentation/Psr6	97.61% <ø> (ø)
Instrumentation/Slim	86.95% <ø> (ø)
Instrumentation/Symfony	89.03% <ø> (ø)
Instrumentation/Yii	77.77% <ø> (ø)
Logs/Monolog	100.00% <ø> (ø)
Propagation/ServerTiming	100.00% <ø> (ø)
Propagation/TraceResponse	100.00% <ø> (ø)
ResourceDetectors/Container	93.02% <ø> (ø)
Shims/OpenTracing	92.99% <ø> (ø)
Symfony	88.20% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 15427f3...86fa1de. Read the comment docs.

[alecsammon]

❤️ - thanks all!