Pin pin_project_lite to older version due to external_type_check compatibility

[lalitb]

Changes

This PR temporarily pins the pin_project_lite crate to version 0.2.14 due to compatibility issues with the external_type_check tool. It seems latest version of pin_project_lite (0.2.15, released today) exposes internal types (e.g., PinnedFieldsOf) in the public API when used in a wrapper struct WithContext, causing external_type_check to fail. This was not an issue in the older version (0.2.14).

CI Error: https://github.com/open-telemetry/opentelemetry-rust/actions/runs/11504205297/job/32023196671?pr=2237

error: Unapproved external type `pin_project_lite::__private::PinnedFieldsOf` referenced in public API
   --> opentelemetry/src/trace/context.rs:363:1
    |
363 | pin_project! {
    | ...
371 | }␊
    | ^
    |
    = in where bound of `opentelemetry::trace::WithContext`

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)

[lalitb]

moving to draft as CI still fails :(

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.5%. Comparing base (2f65b54) to head (6fcc36e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #2239   +/-   ##
=====================================
  Coverage   79.5%   79.5%           
=====================================
  Files        121     121           
  Lines      21113   21113           
=====================================
  Hits       16805   16805           
  Misses      4308    4308           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[lalitb]

ok, this is working now. Have raised an issue in the pin_project_lite repo - taiki-e/pin-project-lite#86