[gcc r16-1035] c++: rename PR120123 test

[Jason Merrill]

https://gcc.gnu.org/g:a0364f41a8a5c9f785da8681c78d22c430ac4d70

commit r16-1035-ga0364f41a8a5c9f785da8681c78d22c430ac4d70
Author: Jason Merrill <jason@redhat.com>
Date:   Sat May 31 23:10:44 2025 -0400

    c++: rename PR120123 test
    
    As Patrick points out (and I had realized after pushing it), this testcase
    has nothing to do with explicit object parameters.
    
            PR c++/120123
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp23/explicit-obj-lambda18.C: Move to...
            * g++.dg/cpp2a/concepts-lambda24.C: ...here.

Diff:
---
 .../g++.dg/{cpp23/explicit-obj-lambda18.C => cpp2a/concepts-lambda24.C} | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda18.C b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda24.C
similarity index 86%
rename from gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda18.C
rename to gcc/testsuite/g++.dg/cpp2a/concepts-lambda24.C
index 21bd2e99e79d..28f56ca2335e 100644
--- a/gcc/testsuite/g++.dg/cpp23/explicit-obj-lambda18.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-lambda24.C
@@ -1,5 +1,5 @@
 // PR c++/120123
-// { dg-do compile { target c++23 } }
+// { dg-do compile { target c++20 } }
 
 struct H {
     void member(int) {}