Productionizing caching section doesn't recommend SQL

[ttomsu]

Page: https://www.spinnaker.io/setup/productionize/caching/configure-redis-usage/

We know from multiple large customers that Redis can only scale so far, so we should be recommending to use the MySQL backends for Clouddriver caching.

Talk to @robzienert for all the gory details

[spinnakerbot]

This issue hasn't been updated in 45 days, so we are tagging it as 'stale'. If you want to remove this label, comment:

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