Fix UNSUPPORTED to exclude C++03 and fix docs

Author: vogelsgesang

libcxx/docs/TestingLibcxx.rst

@@ -451,7 +451,7 @@ Instead use:
 
 .. code-block:: cpp
 
-   // UNSUPPORTED: std-at-least-c++26
+   // REQUIRES: std-at-least-c++26
 
 There is no corresponding ``std-at-most-c++23``. This could be useful when
 tests are only valid for a small set of standard versions. For example, a

libcxx/test/std/language.support/support.exception/propagation/exception_ptr_move_assignment.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: no-exceptions, std-at-least-c++11
+// UNSUPPORTED: no-exceptions, c++03
 
 // <exception>
 

libcxx/test/std/language.support/support.exception/propagation/exception_ptr_move_ctr.pass.cpp

@@ -6,7 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: no-exceptions, std-at-least-c++11
+// UNSUPPORTED: no-exceptions, c++03
 
 // <exception>