mailspring origin header tweak

try.patch

diff --git a/app/internal_packages/onboarding/lib/onboarding-helpers.ts b/app/internal_packages/onboarding/lib/onboarding-helpers.ts
index a83680a21..cc6c6fe8f 100644
--- a/app/internal_packages/onboarding/lib/onboarding-helpers.ts
+++ b/app/internal_packages/onboarding/lib/onboarding-helpers.ts
@@ -88,6 +88,7 @@ async function fetchPostWithFormBody<T>(url: string, body: { [key: string]: stri
       .join('&'),
     headers: {
       'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8',
+      'Origin': 'localhost',
     },
   });
   const json = ((await resp.json()) || {}) as T;