Fix Retry time in Exporter

[ayushtkn]

Describe the bug

After the initial wait, subsequent wait times are randomized within an upper bound, leading to sporadic behavior that deviates from the expected retry pattern.

Related discussion:
#3936 (comment)

Steps to reproduce

• Trigger a retry scenario.
• Note the actual wait times between retries.

What did you expect to see?

The wait times should closely follow the calculated values, with a small and predictable jitter (e.g., 0.2).

What did you see instead?
The wait times are highly variable, appearing random and exceeding the expected jitter tolerance.

What version and what artifacts are you using?
All

Environment
Should be All

Additional context
For reference, see this related gRPC proposal:
grpc/proposal#452