Adjust regex for catching both new and old size error messages

Author: arteam

modules/reindex/build.gradle

@@ -167,7 +167,3 @@ if (OS.current() == OS.WINDOWS) {
     }
   }
 }
-
-tasks.named("yamlRestCompatTestTransform").configure { task ->
-  task.skipTest("reindex/20_validation/specifying size fails", "size is rejected in 9.0")
-}

modules/reindex/src/yamlRestTest/resources/rest-api-spec/test/reindex/20_validation.yml

@@ -94,6 +94,28 @@
         body:
           conflicts: cat
 
+---
+"specifying size fails":
+  - requires:
+      cluster_features: ["gte_v8.0.0"]
+      reason: "size supported until 8"
+
+  - do:
+      index:
+        index:  test
+        id:     "1"
+        body:   { "text": "test" }
+
+  - do:
+      catch: /(invalid parameter \[size\], use \[max_docs\] instead|unknown field \[size\])/
+      reindex:
+        body:
+          source:
+            index: test
+          dest:
+            index: dest
+          size: 1
+
 ---
 "invalid max_docs in body fails":
   - requires: