docs: update image url

Author: Ehesp

docs/image-processing-api/operations.mdx

@@ -532,7 +532,7 @@ Images consisting entirely of a single colour will calculate "boring" using the
 | threshold | Integer |    ✓     |     0     |    n/a    |   n/a   |
 
 export const EXTENSION_URL =
-  'https://europe-central2-dev-extensions-testing.cloudfunctions.net/ext-image-processing-api-handler/process';
+  'https://us-central1-dev-extensions-testing.cloudfunctions.net/ext-image-processing-api-handler/process';
 
 export const IMAGE_URL =
   'https://cdn.pixabay.com/photo/2018/04/29/01/23/skin-3358873_960_720.jpg';