Merge pull request #22856 from github/geoffw0-patch-2

Update instructions for .expected files

Author: geoffw0

.github/instructions/expected-files.instructions.md

@@ -1,4 +1,4 @@
 ---
 applyTo: "**/*.expected"
 ---
-Ignore these files. These are generated to be correct by running the tests, and should not be edited manually.
+Do not edit these files directly. They are generated by running the tests. If a `.expected` file has a non-empty `testFailures `section it should not be committed - you may want to update the inline expectation comments in the corresponding test source file (e.g. marking expected results as `MISSING` / `SPURIOUS`) then re-run the test.