docs: name the parameters these two blocks describe

[darkdi]

This relates to...

Nothing filed, I ran into it while reading the cache store.

Rationale

MemoryCacheStore.get documents its argument as req, while the method takes key and the two neighbours in the same class, createWriteStream and delete, both document key. The webidl one is the more confusing of the two: webidl.errors.exception documents opts, opts.header and opts.message, but the parameter is called message and the body reads message.header and message.message, so the documented name collides with a field name. Its two siblings, conversionFailed and invalidArgument, name the bag opts and context and document exactly that.

Changes

Comments only, no runtime change.

Features

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Bug Fixes

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Breaking Changes and Deprecations

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