testsuite: Uncomment __cpp_consteval test

The __cpp_consteval macro and corresponding test have been initially
commented out because the consteval support didn't have virtual consteval
method support.  The r11-1789-ge6321c4508b2a85c21246c1c06a8208e2a151e48
change enabled the macro but didn't enable the corresponding test.

2021-06-10  Jakub Jelinek  <jakub@redhat.com>

	* g++.dg/cpp2a/feat-cxx2a.C: Uncomment __cpp_consteval test.
	* g++.dg/cpp23/feat-cxx2b.C: Likewise.
diff --git a/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C b/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C
index 4a342e9..283a8ba 100644
--- a/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C
+++ b/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C
@@ -520,13 +520,11 @@
 #  error "__cpp_constexpr_in_decltype != 201711"
 #endif
 
-/* Not supported fully yet:
 #ifndef __cpp_consteval
 #  error "__cpp_consteval"
 #elif __cpp_consteval != 201811
 #  error "__cpp_consteval != 201811"
 #endif
-*/
 
 #ifndef __cpp_concepts
 #  error "__cpp_concepts"
diff --git a/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C b/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C
index dc46e48..3239df8 100644
--- a/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C
+++ b/gcc/testsuite/g++.dg/cpp2a/feat-cxx2a.C
@@ -520,13 +520,11 @@
 #  error "__cpp_constexpr_in_decltype != 201711"
 #endif
 
-/* Not supported fully yet:
 #ifndef __cpp_consteval
 #  error "__cpp_consteval"
 #elif __cpp_consteval != 201811
 #  error "__cpp_consteval != 201811"
 #endif
-*/
 
 #ifndef __cpp_concepts
 #  error "__cpp_concepts"