Fix bad cast in tpu_ext.cc

The argument to the cast value is of type ssize_t. Mismatch between int64_t and ssize_t happens in Mac and causes build to fail:
`error: const_cast from 'const pybind11::ssize_t *' (aka 'const long *') to 'int64_t *' (aka 'long long *') is not allowed`

PiperOrigin-RevId: 584451928

jaxlib/mlir/_mlir_libs/tpu_ext.cc

@@ -576,7 +576,7 @@ PYBIND11_MODULE(_tpu_ext, m) {
           if constexpr (std::is_same_v<ssize_t, int64_t>) {
             // TODO(tlongeri): Find a way to avoid the const_cast
             return mlirTpuAssemble(getDefaultInsertionPoint(), ty, layout,
-                                   {{const_cast<int64_t*>(np_arr.shape()),
+                                   {{const_cast<ssize_t*>(np_arr.shape()),
                                      static_cast<size_t>(np_arr.ndim())},
                                     vals.data()},
                                    TARGET_SHAPE);