LibWeb: Remove unused type XMLHttpRequestBodyInit

Userland/Libraries/LibWeb/Fetch/BodyInit.h

@@ -13,9 +13,6 @@
 
 namespace Web::Fetch {
 
-// https://fetch.spec.whatwg.org/#typedefdef-xmlhttprequestbodyinit
-using XMLHttpRequestBodyInit = Variant<JS::Handle<FileAPI::Blob>, JS::Handle<JS::Object>, JS::Handle<URL::URLSearchParams>, String>;
-
 // https://fetch.spec.whatwg.org/#bodyinit
 using BodyInit = Variant<JS::Handle<Streams::ReadableStream>, JS::Handle<FileAPI::Blob>, JS::Handle<JS::Object>, JS::Handle<URL::URLSearchParams>, String>;