go.mod: upgrade to jsonschema v0.4.1

[jba]

DO NOT SUBMIT

Visible changes:

• Inference on structs populates PropertyOrder

• An empty map for Schema.Properties marshals as "{}"

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net/http: handle foo when bar

[longer description here in the body]

Fixes #12345

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[findleyr]

Hi, is this ready for review? Do we want to land this for v1.2.0-pre.2? It seems like it should land after the v1.2.0 release, given its sensitivity. WDYT?

[jba]

This one was broken. I'll send another one tomorrow or Monday.

I'd be happy to delay it after 1.2.