fix example curl command

[abbbi]

The example curl command shown for the multi file upload example doesnt work, adjust command accordingly.

example wont work:

curl -X POST http://localhost:8080/upload   -F "upload[]=@/tmp/file1"   -F "upload[]=@/tmp/file2"   -H "Content-Type: multipart/form-data"
Uploaded successfully 0 files with fields name= and email=.

working command:

curl -X POST http://localhost:8080/upload   -F "files=@/tmp/file1"   -F "files=@/tmp/file2"   -H "Content-Type: multipart/form-data"
Uploaded successfully 2 files with fields name= and email=.