docs: fix RouteMatrixElement duration return types

[HariNayan]

I have read the CONTRIBUTING.md file.
YES

What kind of change does this PR introduce?
docs update

What is the current behavior?
Closes #16522

The Prisma Quickstart Guide documents RouteMatrixElement.duration
and static_duration as google.protobuf.duration_pb2.Duration,
but at runtime both fields return datetime.timedelta objects.

This mismatch occurs because proto-plus automatically marshals
protobuf Duration types into Python's native datetime.timedelta.

What is the new behavior?
Updated type annotations in routes_service.py:

• duration (google.protobuf.duration_pb2.Duration) → duration (datetime.timedelta)
• static_duration (google.protobuf.duration_pb2.Duration) → static_duration (datetime.timedelta)

Additional context
This is consistent with how proto-plus handles Duration marshalling
across the googleapis Python client libraries. The fix ensures the
documentation matches the actual runtime behavior users observe.

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[gemini-code-assist]

Code Review

This pull request updates the docstrings for the duration and static_duration fields in the RouteMatrixElement class to reflect the use of datetime.timedelta instead of google.protobuf.duration_pb2.Duration. I have no feedback to provide as there were no review comments.

[HariNayan]

@googlebot check cla