remove dead inferred outlives testing code

Author: Lukas Markeffsky

compiler/rustc_error_codes/src/error_codes/E0640.md

@@ -1 +1,2 @@
 #### This error code is internal to the compiler and will not be emitted with normal Rust code.
+#### Note: this error code is no longer emitted by the compiler.

compiler/rustc_hir_analysis/src/lib.rs

@@ -173,12 +173,6 @@ pub fn check_crate(tcx: TyCtxt<'_>) -> Result<(), ErrorGuaranteed> {
         });
     })?;
 
-    if tcx.features().rustc_attrs {
-        tcx.sess.track_errors(|| {
-            tcx.sess.time("outlives_testing", || outlives::test::test_inferred_outlives(tcx));
-        })?;
-    }
-
     tcx.sess.track_errors(|| {
         tcx.sess.time("coherence_checking", || {
             // Check impls constrain their parameters

compiler/rustc_hir_analysis/src/outlives/mod.rs

@@ -9,8 +9,6 @@ use rustc_span::Span;
 
 mod explicit;
 mod implicit_infer;
-/// Code to write unit test for outlives.
-pub mod test;
 mod utils;
 
 pub fn provide(providers: &mut Providers) {

compiler/rustc_hir_analysis/src/outlives/test.rs

@@ -27,7 +27,7 @@ const ERROR_DOCS_PATH: &str = "compiler/rustc_error_codes/src/error_codes/";
 const ERROR_TESTS_PATH: &str = "tests/ui/error-codes/";
 
 // Error codes that (for some reason) can't have a doctest in their explanation. Error codes are still expected to provide a code example, even if untested.
-const IGNORE_DOCTEST_CHECK: &[&str] = &["E0464", "E0570", "E0601", "E0602", "E0640", "E0717"];
+const IGNORE_DOCTEST_CHECK: &[&str] = &["E0464", "E0570", "E0601", "E0602", "E0717"];
 
 // Error codes that don't yet have a UI test. This list will eventually be removed.
 const IGNORE_UI_TEST_CHECK: &[&str] =