test: remove middie usage

[Fdawgs]

Used in tests but not explicitly defined as dependency:

fastify-request-context/index.test-d.ts

Line 11 in 9524b32

const middie = require('middie')

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[kibertoad]

I don't think we actually need middie there, I assume we can just drop it instead

[climba03003]

middie added on #7
Maybe just an issue of copy and paste.

[kibertoad]

yeah, there is even a comment thread on that PR discussing how middie is not needed