fix(instrumentation-aws-lambda): Change endSpan error-logs for forceflush into debug-logs

[jj22ee]

Which problem is this PR solving?

• instrumentation-aws-lambda: Error when configuring tracing without metrics #2747

Short description of the changes

• This log is not an actual error, because it is really just a warning. Thus, change it to debug log.
  • It could be argued that this could be warn log instead, but given the default info log level, these logs appear in each Lambda invocation when TracerProvider and/or MeterProvider are not configured, which is a bit noisy for logs.

[pichlermarc]

thanks! 🙂

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.53%. Comparing base (b520d04) to head (9d40386).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2753   +/-   ##
=======================================
  Coverage   91.53%   91.53%           
=======================================
  Files         171      171           
  Lines        8172     8172           
  Branches     1660     1660           
=======================================
  Hits         7480     7480           
  Misses        692      692           

Files with missing lines	Coverage Δ
...-instrumentation-aws-lambda/src/instrumentation.ts	94.52% <100.00%> (ø)

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