Version up sample code/Cargo.toml on README.md

[Shunpoco]

Changes

This PR modifies some problems in the sample code on README 😸 :

• TracerProvider in v0.22 doesn't have shutdown() method. We should use v0.27 (the latest version) instead
• opentelemetry::global is no longer used since 6d1a765
• opentelemetry-stdout v0.3 is outdated. It's SpanExporter doesn't satisfy with_simple_exporter()'s requirement

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.5%. Comparing base (a1860eb) to head (8ab6018).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2585   +/-   ##
=====================================
  Coverage   79.5%   79.5%           
=====================================
  Files        118     118           
  Lines      22490   22490           
=====================================
  Hits       17888   17888           
  Misses      4602    4602           

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[lalitb]

Thanks.