fix: update functions template to remove deprecated serve

[eifr]

What kind of change does this PR introduce?

update template of new function as serve from http/server.ts is deprecated.

What is the current behavior?

import { serve } from "https://deno.land/std@0.201.0/http/server.ts"; is being used to serve

What is the new behavior?

Deno.serve() will be used for functions as it's what recommended from Deno

[coveralls]

Pull Request Test Coverage Report for Build 6232743560

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.03%) to 56.661%

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Files with Coverage Reduction	New Missed Lines	%
internal/gen/keys/keys.go	5	12.31%

Totals
Change from base Build 6232695550:	-0.03%
Covered Lines:	4985
Relevant Lines:	8798

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💛 - Coveralls

[laktek]

Nice! thanks for the contribution @eifr