[iris.ci] environment lockfiles auto-update

[scitools-ci[bot]]

Lockfiles updated to the latest resolvable environment.

If the CI tasks fail, create a new branch based on this PR and add the required fixes to that branch.

[bjlittle]

@rcomer ... and here's the test failure, as expected.

I'll take a look at this and ping you on it :+1:

[trexfeathers]

Since the failure concerns deprecated API, and since the test's design is questionable, several of us are in favour of skipping this test until the deprecation runs its course:

• @trexfeathers
• @rcomer
• @bsherratt
• @bjlittle?

[rcomer]

See #4901.