docs: clarify unit for OTEL_EXPORTER_OTLP_TIMEOUT default

[ta-ke-inf]

Description

Clarify the unit for the documented default value of OTEL_EXPORTER_OTLP_TIMEOUT in the SDK environment variables docs.

The current docs show Default: 10 without stating the unit, which can lead to operators misinterpreting the value (e.g., 10ms vs 10s). This PR updates only the default line to make the unit explicit while keeping the surrounding wording consistent with existing env var docs.

Fixes #4858

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Built the docs locally with Sphinx

Repro steps:

• python -m pip install -r docs-requirements.txt
• cd docs && python -m sphinx -b html -D master_doc=sdk/environment_variables . _build/html_envvars

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated (not needed for docs-only clarification)
• Unit tests have been added (not applicable)
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ta-ke-inf / name: Takeguchi (3aa10ad, 90b122b, a2a2ddf)

[emdneto]

This reminded me that we need to update matrix compliance #4044 (comment)

I think it is worth having a quick note on this env var stating it is not compliant and referring to #4044.

[ta-ke-inf]

@emdneto

a2a2ddf

Thank you! As also mentioned in #4044, it seems that OTEL_EXPORTER_OTLP_TIMEOUT currently needs to be specified in milliseconds, so to avoid confusion I propose updating the documentation to use 10000 instead of 10 for now.