Container Sharding in Swift suggested doc update

[Laura Marsh]

This bug tracker is for errors with the documentation, use the following as a template and remove or add fields as you see fit. Convert [ ] into [x] to check boxes:

- [x ] I have a fix to the document that I can paste below including example: input and output.

We talked at PTG about wanting to rewrite the container sharding note & get ride of the "experimental" wording. I suggest the following:

"Container sharding is an advanced process. At this time, how to reverse the sharding process once sharding is enabled is not documented. Become proficient with the process on non-production clusters prior to sharding containers in a production environment.

Container sharding involves moving container database records via the container replication engine. The time it takes to completely shard a container depends on the existing cluster load and the performance of the container database being sharded."

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Release: 2.28.0.dev87 on 2020-01-06 10:34:42
SHA: be0f6fee7cdefb60fd28f5d5298c06d1be6832cd
Source: https://opendev.org/openstack/swift/src/doc/source/overview_container_sharding.rst
URL: https://docs.openstack.org/swift/latest/overview_container_sharding.html