[Cpp] Constant presence field should also be not be SBE_NOEXCEPT for compatibility with schema change. PR #806.

Author: mjpt777

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java

@@ -2251,7 +2251,7 @@ private void generateEnumProperty(
                 constValue.substring(constValue.indexOf(".") + 1));
 
             new Formatter(sb).format("\n" +
-                indent + "    SBE_NODISCARD %1$s::Value %2$s() const SBE_NOEXCEPT\n" +
+                indent + "    SBE_NODISCARD %1$s::Value %2$s() const\n" +
                 indent + "    {\n" +
                 "%3$s" +
                 indent + "        return %1$s::Value::%4$s;\n" +