fix: Change Content-Type header to respect RFC 7231 (#7690)

Co-authored-by: João Maridalho <[email protected]>

Author: joaomaridalho

.changeset/brown-moons-yawn.md

@@ -0,0 +1,5 @@
+---
+'@builder.io/qwik-city': patch
+---
+
+fix: Change Content-Type header in qwik requests to respect RFC 7231

packages/qwik-city/src/runtime/src/use-endpoint.ts

@@ -115,7 +115,7 @@ const getFetchOptions = (
       method: 'POST',
       body: JSON.stringify(actionData),
       headers: {
-        'Content-Type': 'application/json, charset=UTF-8',
+        'Content-Type': 'application/json; charset=UTF-8',
       },
     };
   }