Fix jest/matchers/toWarnDev expected, actual order for jest-diff (#12285) (#12288)

`toWarnDev` calls `jestDiff(a, b)` which calls `diffStrings(a, b)` where by default `a` is annotated as `'Expected'` (green), `b` as `'Received'` (red).

So the first argument passed into `jestDiff` should be the expected message, the second should be the actual message.
It was vice versa previously.

- https://github.com/facebook/jest/blob/457776b2889a9be1ce8a2c636a23417264a98d99/packages/jest-diff/src/index.js#L54
- https://github.com/facebook/jest/blob/457776b2889a9be1ce8a2c636a23417264a98d99/packages/jest-diff/src/index.js#L93
- https://github.com/facebook/jest/blob/457776b2889a9be1ce8a2c636a23417264a98d99/packages/jest-diff/src/diff_strings.js#L249-L251

scripts/jest/matchers/toWarnDev.js

@@ -49,11 +49,11 @@ const createMatcherFor = consoleMethod =>
         } else if (expectedMessages.length === 1) {
           errorMessage =
             'Unexpected warning recorded: ' +
-            jestDiff(normalizedMessage, expectedMessages[0]);
+            jestDiff(expectedMessages[0], normalizedMessage);
         } else {
           errorMessage =
             'Unexpected warning recorded: ' +
-            jestDiff([normalizedMessage], expectedMessages);
+            jestDiff(expectedMessages, [normalizedMessage]);
         }
 
         // Record the call stack for unexpected warnings.