fix: remove unused jsonp delegate

[dead-horse]

Checklist

• npm test passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

[mention-bot]

@dead-horse, thanks for your PR! By analyzing the history of the files in this pull request, we identified @fengmk2, @popomore and @atian25 to be potential reviewers.

[codecov]

Codecov Report

Merging #739 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #739   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          26     26           
  Lines         640    640           
=====================================
  Hits          640    640

Impacted Files	Coverage Δ
app/extend/context.js	100% <ø> (ø)	⬆️

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[fengmk2]

jsonp is a middleware now.