remove confusing message Successfully sent cached envelope

[SimonCropp]

In the CachingTransport we have:

_options.LogDebug("Sending cached envelope: {0}", envelope.TryGetEventId());

await _innerTransport.SendEnvelopeAsync(envelope, cancellation).ConfigureAwait(false);

_options.LogDebug("Successfully sent cached envelope: {0}", envelope.TryGetEventId());

But inside the HttpTransport we have:

if (response.StatusCode != HttpStatusCode.OK)
{
    await HandleFailureAsync(response, processedEnvelope, cancellationToken).ConfigureAwait(false);
    return;
}

So for error response codes (eg bad payloads like #1523 ) it is swallowed.

so the diagnostic log says

Sending cached envelope: ...
Sentry rejected the envelope...
Successfully sent cached envelope...

IMO since HttpTransport does a Envelope '{0}' sent successfully on success. the CachingTransport Successfully sent is redundant on success, and misleading on failure.

[codecov-commenter]

Codecov Report

Merging #1542 (1c816d4) into main (341087d) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1542      +/-   ##
==========================================
- Coverage   84.32%   84.30%   -0.02%     
==========================================
  Files         219      219              
  Lines        7418     7417       -1     
  Branches     1418     1418              
==========================================
- Hits         6255     6253       -2     
  Misses        736      736              
- Partials      427      428       +1     

Impacted Files	Coverage Δ
src/Sentry/Internal/Http/CachingTransport.cs	79.16% <ø> (-0.15%)	⬇️
src/Sentry/Exceptions/SentryStackFrame.cs	76.92% <0.00%> (-1.10%)	⬇️

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