Remove some legacy test suites.

src/compiletest.md

@@ -16,9 +16,9 @@ and more. If you are unfamiliar with the compiler testing framework,
 see [this chapter](./tests/intro.md) for additional background.
 
 The tests themselves are typically (but not always) organized into
-"suites" – for example, `run-fail`, a folder holding tests that should compile
-successfully, but return a failure (non-zero status) at runtime, `compile-fail`,
-a folder holding tests that should fail to compile, and many more. The various
+"suites" – for example, `incremental`, a folder holding tests that check
+incremental compilation behavior, `codegen`,
+a folder holding tests that check code generation, and many more. The various
 suites are defined in [`src/tools/compiletest/src/common.rs`] in the
 `pub enum Mode` declaration. And a good introduction to the different
 suites of compiler tests along with details about them can be found in

src/tests/adding.md

@@ -43,7 +43,6 @@ rough heuristics:
     message is not relevant to the test. These should have an
     [error number] (`E0XXX`) in the code block to make sure it's the correct error.
 - For most other things, [a `ui` (or `ui-fulldeps`) test](#ui) is to be preferred:
-  - [`ui`](#ui) tests subsume both `run-pass`, `compile-fail`, and `parse-fail` tests
   - in the case of warnings or errors, `ui` tests capture the full output,
     which makes it easier to review but also helps prevent "hidden" regressions
     in the output