[version.syn] Bump value of __cpp_lib_constexpr_cmath

Author: tkoeppe

source/support.tex

@@ -600,7 +600,7 @@
 #define @\defnlibxname{cpp_lib_constexpr_algorithms}@              202306L // also in \libheader{algorithm}, \libheader{utility}
 #define @\defnlibxname{cpp_lib_constexpr_bitset}@                  202207L // also in \libheader{bitset}
 #define @\defnlibxname{cpp_lib_constexpr_charconv}@                202207L // also in \libheader{charconv}
-#define @\defnlibxname{cpp_lib_constexpr_cmath}@                   202202L // also in \libheader{cmath}, \libheader{cstdlib}
+#define @\defnlibxname{cpp_lib_constexpr_cmath}@                   202306L // also in \libheader{cmath}, \libheader{cstdlib}
 #define @\defnlibxname{cpp_lib_constexpr_complex}@                 201711L // also in \libheader{complex}
 #define @\defnlibxname{cpp_lib_constexpr_dynamic_alloc}@           201907L // also in \libheader{memory}
 #define @\defnlibxname{cpp_lib_constexpr_functional}@              201907L // freestanding, also in \libheader{functional}