Fix examples after C2x renaming

This amends 0ce056a and fixes an
example that was not built locally for me.

Author: AaronBallman

clang/examples/Attribute/Attribute.cpp

@@ -29,10 +29,10 @@ struct ExampleAttrInfo : public ParsedAttrInfo {
     // number of arguments. This just illustrates how many arguments a
     // `ParsedAttrInfo` can hold, we will not use that much in this example.
     OptArgs = 15;
-    // GNU-style __attribute__(("example")) and C++/C2x-style [[example]] and
+    // GNU-style __attribute__(("example")) and C++/C23-style [[example]] and
     // [[plugin::example]] supported.
     static constexpr Spelling S[] = {{ParsedAttr::AS_GNU, "example"},
-                                     {ParsedAttr::AS_C2x, "example"},
+                                     {ParsedAttr::AS_C23, "example"},
                                      {ParsedAttr::AS_CXX11, "example"},
                                      {ParsedAttr::AS_CXX11, "plugin::example"}};
     Spellings = S;