Don't suggest cache tags for Redis

[dbhynds]

The upgrade guide indicates that Redis cache tags got a performance improvement. However based on discussions linked below, it appears that usage of redis cache tags is not recommended. The outdated guidance in the upgrade guide caused a series of significant bugs in our production application. This PR updates the docs to recommend against using cache tags until a suitable solution can be found.

• Discussion of the problem: Revert Redis Tagged cache implementation framework#49159
• Evidence that redis cache tagging isn't coming back or getting fixed any time soon: [10.x] Use Lua script in Redis to flush cache tags atomically framework#48078 (comment)

The current upgrade guide still contains a broken link to the documentation on cache tagging (which was removed as a result of Taylor's comment in the second link there).

If there is another recommended way for implementing Redis cache tags, I'd be happy to write up docs for that, but I'm not seeing one in my quick perusal of the issues, PRs, and conversations in github.

[taylorotwell]

@dbhynds Are you able to test the changes in laravel/framework#48078 to see if it fixes your issues?

[dbhynds]

I'll need some time to look into that question. We didn't see the problem in any of our pre-production environments or manual testing. The associated bug in our app was only discovered in prod. So I'm going to need some time to figure out how to duplicate it locally. That said, I'll try to carve out some time in the next week or two to try out that PR and see if it works.