release-24.2: sql/catalog/bootstrap: don't call PrefixEnd on tenant start key

[blathers-crl]

Backport 1/1 commits from #131208 on behalf of @stevendanna.

/cc @cockroachdb/release

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KVServer expects that split keys have a valid tenant prefix. Calling PrefixEnd() on the start key to a tenant does not produce a valid key as the tenant ID is encoded as a varint.

Epic: none
Release note: None

---

Release justification: Low risk bug fix for tenant-creation stopping bug

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
• Backports should not break backwards-compatibility.
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  here).
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  policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• 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).
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Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[jeffswenson]

LGTM

[github-actions]

Reminder: it has been 3 weeks please merge or close your backport!