fix: test were broken due to wrong json fixture

Author: ahmadnassri

test/fixtures/files/hello.txt

@@ -0,0 +1 @@
+Hello World

test/fixtures/output/curl/multipart-file.sh

@@ -1,4 +1,4 @@
 curl --request POST \
   --url "http://mockbin.com/har" \
   --header "Content-Type: multipart/form-data" \
-  --form "foo=hello world"
+  --form "foo=Hello World"

test/fixtures/output/httpie/multipart-file.sh

@@ -1,3 +1,3 @@
 http POST http://mockbin.com/har \
   Content-Type:multipart/form-data \
-  foo:hello world
+  foo:Hello World

test/fixtures/output/ocaml/cohttp/multipart-file.ml

@@ -5,7 +5,7 @@ let uri = Uri.of_string "http://mockbin.com/har" in
 let headers = Header.init ()
   |> fun h -> Header.add h "Content-Type" "multipart/form-data"
 in
-let body = "foo=hello world" in
+let body = "foo=Hello World" in
 
 Client.call ~headers ~body (Code.method_of_string "POST") uri
 >>= fun (res, body_stream) ->

test/fixtures/requests/multipart-file.json

@@ -12,7 +12,8 @@
     "params": [
       {
         "name": "foo",
-        "fileName": "fixtures/files/hello.txt",
+        "value": "Hello World",
+        "fileName": "hello.txt",
         "contentType": "text/plain"
       }
     ]