docs: fix links to the non-existent examples/tutorials directory

[ankitranjan-dsai]

Closes #1905.

Docs only — no code, no tests affected.

Problem

examples/README.md documents a tutorials folder and links to examples/tutorials/, which does not exist on main (gh api .../contents/examples/tutorials → 404). Three references are dead:

• examples/README.md:26 — the folder-structure entry
• examples/README.md:43 — the "How to use these examples" bullet
• examples/cookbook/README.md:30 — "the tutorials directory"

Every other folder-structure entry (cookbook, service, grafana, datasets) resolves fine.

Why this fix rather than adding the folder

The tutorials are not missing — they are at the examples/ root. The same README already calls them that at line 7 ("start with these three top-level tutorials") and at line 41, linking agentic_systems_tracing.ipynb, llm_input_output_validation.ipynb and classic_ml_validation.ipynb directly.

eb5d82a (#1853) created the README and those three notebooks in one commit, moving examples/cookbook/tracing_with_service.ipynb up to examples/agentic_systems_tracing.ipynb. No tutorials/ directory was created or renamed away there, so the entry looks like a description of a layout that was not used.

Changes

• examples/README.md — the folder-structure entry now points at the top-level tutorials (anchor link to the existing Start here section) and says where they live.
• examples/README.md — dropped the tutorials bullet under "How to use these examples"; with the phantom folder gone it just restated the top-level-tutorials bullet directly above it.
• examples/cookbook/README.md — same reference repointed at Start here, keeping the existing examples folder link.

Wording is otherwise the authors’ own; no reflow, no trailing-newline changes.

Verification

Resolved every markdown link in both files, GitHub-style (leading / against repo root, otherwise relative to the file), and checked the two #start-here anchors against the actual headings:

examples/README.md              8 links   8 pass   (incl. #start-here)
examples/cookbook/README.md    12 links  12 pass   (incl. ../README.md#start-here)

A repo-wide sweep of all 15 markdown files now reports 0 broken relative links; before this change it reported the 2 above.

If you would prefer an actual examples/tutorials/ directory instead, say so and I will close this.