release-22.1: cli: Disable multi-tenancy demo by default

[ajstorm]

Backport 1/1 commits from #78018.

/cc @cockroachdb/release

---

In #71988 we enabled multi-tenancy by default as a means to draw out
gaps when running in that mode. That effort was largely successful, and
identified several issues which are now on the MT team's backlog. Unfortunately
however, we weren't able to resolve all of these issues in time for the 22.1
release. As a result, we're now disabling multi-tenancy by default in 22.1. We
will try to enable it again on master once this change is backported so that we
can continue testing in this mode by default.

Release note (cli change): cockroach demo is reverted back to not run
multi-tenant mode by default.

Release justification: Reverting new functionality.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Patches should only be created for serious issues or test-only changes.
• Patches should not break backwards-compatibility.
• Patches should change as little code as possible.
• Patches should not change on-disk formats or node communication protocols.
• Patches should not add new functionality.
• Patches must not add, edit, or otherwise modify cluster versions; or add version gates.

If some of the basic criteria cannot be satisfied, ensure that the exceptional criteria are satisfied within.

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
• The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting).
• New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters.
• The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules.

Add a brief release justification to the body of your PR to justify this backport.

Some other things to consider:

• What did we do to ensure that a user that doesn’t know & care about this backport, has no idea that it happened?
• Will this work in a cluster of mixed patch versions? Did we test that?
• If a user upgrades a patch version, uses this feature, and then downgrades, what happens?

[cockroach-teamcity]

This change is 

[jordanlewis]

LGTM