refactor(aws-lambada): remove FIXME in @ts-expect-error

[yusukebe]

@ts-expect-error is not bad. We don't have to "fix it"; if so, the type definition, which does not affect users, will be fat.

Closes #5123

The author should do the following, if applicable

• Add tests
• Run tests
• bun run format:fix && bun run lint:fix to format the code
• Add TSDoc/JSDoc to document the code

[github-actions]

HTTP Performance Benchmark

Framework	Runtime	Average	Ping	Query	Body
hono (origin/main)	bun	35,991.99	50,665.16	31,735.12	25,575.70
hono (current)	bun	36,513.67	51,643.27	32,301.28	25,596.47
Change		+1.45%	+1.93%	+1.78%	+0.08%

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.08%. Comparing base (c285f9a) to head (027fb15).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5130   +/-   ##
=======================================
  Coverage   79.08%   79.08%           
=======================================
  Files         154      154           
  Lines       10764    10764           
  Branches     2254     2254           
=======================================
  Hits         8513     8513           
  Misses       2251     2251           

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