docs: Don't unnecessarily show simpleexporter in OTLP docs

[cijothomas]

Show the recommended option in the doc, instead of showing simple_exporter and then telling few lines down that it is not recommended! All examples of OTLP are already using batch-exporter only.

Keeping simple_exporter to truly getting-started guides, that uses stdout is better.

[Copilot]

Pull Request Overview

This PR updates the OpenTelemetry OTLP documentation to show best practices by default, replacing with_simple_exporter with with_batch_exporter in all code examples and removing a redundant performance section that explained why batch exporters are preferred.

• Updated three code examples to use with_batch_exporter instead of with_simple_exporter
• Removed the "Performance" section that contained redundant information about batch vs simple exporters

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.5%. Comparing base (4486207) to head (e2e7a5a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3105     +/-   ##
=======================================
- Coverage   80.5%   80.5%   -0.1%     
=======================================
  Files        126     126             
  Lines      22218   22218             
=======================================
- Hits       17890   17889      -1     
- Misses      4328    4329      +1     

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