storage: don't import testing for DisableMetamorphicSimpleValueEncoding

[erikgrinaker]

We shouldn't link testing in binaries.

Epic: none
Release note: None

[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[erikgrinaker]

@rickystewart Didn't we use to lint against importing certain packages in production code?

[rickystewart]

@rickystewart Didn't we use to lint against importing certain packages in production code?

"Technically", the test existed and was deleted by me. Due to bitrot the assertion broke years ago. I think the breakage may have predated my time at CRL but definitely occurred in non-Bazel CI in addition to Bazel CI, where the test itself doesn't make much sense either way.

We're in need of a new linter for this: #81526

[erikgrinaker]

bors r+

[craig]

This PR was included in a batch that successfully built, but then failed to merge into master (it was a non-fast-forward update). It will be automatically retried.

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)