fix(stdlib): Fix parsing nginx error log delaying request

[JakubOnderka]

Summary

parse_nginx_log can currently successfully parse limiting requests log, but delaying requests has little bit different and contains one extra comma.

2022/05/30 20:56:22 [error] 7164#7164: *38068741 limiting requests, excess: 50.416 by zone "api_access_token"
2022/05/30 20:56:22 [error] 7164#7164: *38068741 delaying requests, excess: 50.416, by zone "api_access_token"

https://github.com/nginx/nginx/blob/d25139db01b636a8212c13e1feeca37eaadad0b5/src/http/modules/ngx_http_limit_req_module.c#L301

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Standard test case.

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on
  our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Our CONTRIBUTING.md is a good starting place.
• If this PR introduces changes to LICENSE-3rdparty.csv, please
  run dd-rust-license-tool write and commit the changes. More details here.
• For new VRL functions, please also create a sibling PR in Vector to document the new function.

[pront]

Thank you @JakubOnderka