Downgrade dependency mongodb to 3.6.11 to fix incompatibility issue with v4+

Editor assessment

The reasoning is good — pinning mongodb to 3.6.11 because v4+ is incompatible is exactly what a changelog reader wants to know — but the execution overloads the subject. At roughly 90 characters with the type and scope, it far exceeds the 72-character ceiling, and `to fix incompatibility issue` duplicates the `fix` type already stated. Better: subject `fix(samples): downgrade mongodb to 3.6.11` with a body explaining the v4 incompatibility and a `Refs` footer to the tracking issue. The `samples` scope is well chosen for a monorepo. With no body, the workaround rationale lives only in this stretched header. Not breaking to library consumers; patch-level.