Summary:
This diff removes the code which creates a request scope for CDC reads. This request_scope
is not requirred for the reads performed by CDC.
Jira: DB-14510

Test Plan:
Jenkins: test regex: .*CDC.*
Existing CDC tests. Also verified manually that untracked memory does not increase after this
change.

Reviewers: skumar, siddharth.shah

Reviewed By: skumar

Subscribers: ycdcxcluster

Differential Revision: https://phorge.dev.yugabyte.com/D40708