fix(proxy): respect fetchOptions.method over incoming request method

[emilsgulbis]

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

When proxyRequest is used with different method (e.g. GET) defined in fetchOptions, the body is still filled and returns Request with GET/HEAD method cannot have body.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[nozomuikuta]

@emilsgulbis

Would you add unit test?
https://github.com/unjs/h3/blob/main/test/proxy.test.ts

[codecov]

Codecov Report

Merging #441 (50697f8) into main (d11f817) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #441   +/-   ##
=======================================
  Coverage   77.74%   77.74%           
=======================================
  Files          26       26           
  Lines        2692     2692           
  Branches      393      394    +1     
=======================================
  Hits         2093     2093           
  Misses        599      599           

Impacted Files	Coverage Δ
src/utils/proxy.ts	81.51% <100.00%> (ø)

[pi0]

Thanks!

[pi0]

Adding an additional test would be nice btw (however is not necessary)