fix(android): UTF-8 encode form data value (#7531)

Co-authored-by: Malo <55086681+malo-malo@users.noreply.github.com>
Co-authored-by: Malo <malo.c@hellowatt.fr>

android/capacitor/src/main/java/com/getcapacitor/plugin/util/CapacitorHttpUrlConnection.java

@@ -275,7 +275,7 @@ private void writeFormDataRequestBody(String contentType, JSArray entries) throw
                     if (type.equals("string")) {
                         os.writeBytes(twoHyphens + boundary + lineEnd);
                         os.writeBytes("Content-Disposition: form-data; name=\"" + key + "\"" + lineEnd + lineEnd);
-                        os.writeBytes(value);
+                        os.write(value.getBytes(StandardCharsets.UTF_8));
                         os.writeBytes(lineEnd);
                     } else if (type.equals("base64File")) {
                         String fileName = entry.getString("fileName");