rename some issues-* tests

src/tools/tidy/src/issues.txt

@@ -117,7 +117,6 @@ ui/associated-types/issue-44153.rs
 ui/associated-types/issue-47139-1.rs
 ui/associated-types/issue-47139-2.rs
 ui/associated-types/issue-47385.rs
-ui/associated-types/issue-47814.rs
 ui/associated-types/issue-48010.rs
 ui/associated-types/issue-48551.rs
 ui/associated-types/issue-50301.rs
@@ -406,7 +405,6 @@ ui/closures/2229_closure_analysis/match/issue-87097.rs
 ui/closures/2229_closure_analysis/match/issue-87426.rs
 ui/closures/2229_closure_analysis/match/issue-87988.rs
 ui/closures/2229_closure_analysis/match/issue-88331.rs
-ui/closures/2229_closure_analysis/migrations/issue-78720.rs
 ui/closures/2229_closure_analysis/migrations/issue-86753.rs
 ui/closures/2229_closure_analysis/migrations/issue-90024-adt-correct-subst.rs
 ui/closures/2229_closure_analysis/run_pass/issue-87378.rs
@@ -1001,7 +999,6 @@ ui/fmt/issue-86085.rs
 ui/fmt/issue-89173.rs
 ui/fmt/issue-91556.rs
 ui/fn/issue-1451.rs
-ui/fn/issue-1900.rs
 ui/fn/issue-3044.rs
 ui/fn/issue-3099.rs
 ui/fn/issue-3904.rs

tests/ui/closures/2229_closure_analysis/migrations/nested-copy-drops-83176.rs

@@ -1,3 +1,4 @@
+// Regression test for https://github.com/rust-lang/rust/issues/83176.
 //@ run-pass
 
 #![warn(rust_2021_incompatible_closure_captures)]

tests/ui/closures/2229_closure_analysis/migrations/nested-copy-drops-83176.stderr

@@ -1,5 +1,5 @@
 warning: irrefutable `if let` pattern
-  --> $DIR/issue-78720.rs:7:8
+  --> $DIR/nested-copy-drops-83176.rs:8:8
    |
 LL |     if let a = "" {
    |        ^^^^^^^^^^

tests/ui/impl-trait/rpit/unit-impl-default-36379.rs

@@ -0,0 +1,6 @@
+//! Regression test for https://github.com/rust-lang/rust/issues/36379
+//@ check-pass
+
+fn _test() -> impl Default { }
+
+fn main() {}

tests/ui/issues/issue-36379.rs

@@ -1,5 +0,0 @@
-//@ check-pass
-
-fn _test() -> impl Default { }
-
-fn main() {}