Fix compilation with GCC 8 (#1051)

The anonymous namespace was renamed due to -Wsubobject-linkage complaining
about a field created in a GTest template class (CborRoundtripTestParam)
being defined in an anonymous namespace. See
https://stackoverflow.com/a/37723265.

wpiutil/src/test/native/cpp/json/unit-unicode.cpp

@@ -70,7 +70,7 @@ using wpi::json;
 
     try {
         json::parse(json_string);
-    } catch (json::parse_error) {
+    } catch (json::parse_error&) {
         if (success_expected)
         {
             basemsg = "parse_error";