fix: forward x-audit-log-reason header

[NickantX]

Please describe the changes this PR makes and why it should be merged:

Resolves an issue with djs/proxy where the X-Audit-Log-Reason header was not being forwarded, preventing audit log reasons from appearing for any requests that specified them.

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• I know how to update typings and have done so, or typings don't need updating

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

2 Ignored Deployments

Name	Status	Preview	Comments	Updated (UTC)
discord-js	⬜️ Ignored (Inspect)	Visit Preview		Oct 15, 2023 10:39pm
discord-js-guide	⬜️ Ignored (Inspect)	Visit Preview		Oct 15, 2023 10:39pm

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	72
🟢 Accessibility	96
🟢 Best practices	100
🟠 SEO	67
🔴 PWA	33

Lighthouse ran on https://discord-js-guide-git-fork-nickantx-main-discordjs.vercel.app/

[codecov]

Codecov Report

Merging #9889 (67799c8) into main (8964504) will decrease coverage by 0.01%.
The diff coverage is 25.00%.

@@            Coverage Diff             @@
##             main    #9889      +/-   ##
==========================================
- Coverage   60.05%   60.04%   -0.01%     
==========================================
  Files         235      235              
  Lines       16023    16027       +4     
  Branches     1215     1216       +1     
==========================================
+ Hits         9623     9624       +1     
- Misses       6356     6359       +3     
  Partials       44       44              

Flag	Coverage Δ
proxy	75.00% <25.00%> (-1.32%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
packages/proxy/src/handlers/proxyRequests.ts	73.84% <25.00%> (-3.21%)	⬇️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more