enhance(backend): use native fetch instead of node-fetch polyfill

[syuilo]

What

Node.js v18から標準でfetchが実装されたのでポリフィルを使う必要がなくなった

Why

Additional info (optional)

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.98%. Comparing base (73cc30f) to head (d26dab8).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop   #16964       +/-   ##
============================================
+ Coverage    13.97%   60.98%   +47.00%     
============================================
  Files          237     1150      +913     
  Lines        11272   115218   +103946     
  Branches      3727     7584     +3857     
============================================
+ Hits          1575    70263    +68688     
- Misses        7577    42793    +35216     
- Partials      2120     2162       +42     

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[github-actions]

このPRによるapi.jsonの差分
差分はありません。
Get diff files from Workflow Page

[github-actions]

Backend Memory Usage Comparison

Metric	base	head	Diff
RSS	359.37 MB	356.74 MB	-2.63 MB (-.73%)

See workflow logs for details

[kakkokari-gtyih]

たぶんagentが指定できない

[syuilo]

👀
https://stackoverflow.com/questions/73817412/why-is-the-agent-option-not-available-in-node-native-fetch

[syuilo]

https://yosuke-furukawa.hatenablog.com/entry/2022/12/05/103008

[syuilo]

あとsizeがないって言われてる