docs: add :scm_web: links to example README files referencing source code

[harshitnagar22]

What

Added :scm_web: links to 6 README.rst files under docs/examples/ so the rendered docs link back to the actual source files on GitHub.

Why

Fixes #5427 — some example README pages on Read the Docs list Python files but don't link them, making it hard for users to find the actual source code.

Changes

File	Change
docs/examples/auto-instrumentation/README.rst	Added :scm_web: link
docs/examples/error_handler/error_handler_0/README.rst	Added :scm_web: link
docs/examples/error_handler/error_handler_1/README.rst	Added :scm_web: link
docs/examples/fork-process-model/flask-gunicorn/README.rst	Added :scm_web: link
docs/examples/fork-process-model/flask-uwsgi/README.rst	Added :scm_web: link
docs/examples/sqlcommenter/README.rst	Replaced hardcoded GitHub URL with :scm_web:

Follows the same pattern used in docs/examples/django/README.rst.

[linux-foundation-easycla]

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• ✅ login: harshitnagar22 / name: Harshit Nagar (02137cf, 677684b)

[AJ-ing]

Thanks for tackling #5427!

I audited docs/examples on current main: the only READMEs still missing :scm_web: are exactly the six files in this PR (auto-instrumentation, sqlcommenter, error_handler_{0,1}, flask-gunicorn, flask-uwsgi). The parent examples already link correctly.

One nit for consistency with docs/examples/django/README.rst / metrics/views/README.rst: prefer :scm_web: links over raw GitHub URLs where possible (sqlcommenter currently uses a raw link on main).

I'll stay out of the way so maintainers can pick one complete PR among #5428 / #5429 / #5433.