Disable merged doctests by default

Author: GuillaumeGomez

src/librustdoc/doctest.rs

@@ -772,7 +772,7 @@ struct CreateRunnableDoctests {
 
 impl CreateRunnableDoctests {
     fn new(rustdoc_options: RustdocOptions, opts: GlobalTestOptions) -> CreateRunnableDoctests {
-        let can_merge_doctests = true; //rustdoc_options.edition >= Edition::Edition2024;
+        let can_merge_doctests = rustdoc_options.edition >= Edition::Edition2024;
         CreateRunnableDoctests {
             standalone_tests: Vec::new(),
             mergeable_tests: FxHashMap::default(),

tests/rustdoc-ui/doctest/failed-doctest-should-panic.stdout

@@ -5,7 +5,6 @@ test $DIR/failed-doctest-should-panic.rs - Foo (line 9) - should panic ... FAILE
 failures:
 
 ---- $DIR/failed-doctest-should-panic.rs - Foo (line 9) stdout ----
-Hello, world!
 note: test did not panic as expected
 
 failures: