fix(core): Fix our array returns (#3696)

.changeset/thin-cougars-give.md

···
+---
+'@urql/core': patch
+---
+
+Fix `deepMerge` regression on array values

packages/core/src/utils/result.ts

···
       target = [...target];
       for (let i = 0, l = source.length; i < l; i++)
         target[i] = deepMerge(target[i], source[i]);
+
+      return target;
     }
-    if (
-      !target.constructor ||
-      target.constructor === Object ||
-      Array.isArray(target)
-    ) {
+    if (!target.constructor || target.constructor === Object) {
       target = { ...target };
       for (const key in source)
         target[key] = deepMerge(target[key], source[key]);