Remove cssx.sx references from WASM test scripts

cssx.sx was deleted in the CSSX → ~tw migration. The test scripts
(test_wasm.sh, test_wasm_native.js, bisect_sxbc.sh) still referenced
it, causing ENOENT during WASM build step 5.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/browser/test_wasm.sh

@@ -211,7 +211,6 @@ node -e '
     "shared/static/wasm/sx/adapter-html.sx",
     "shared/static/wasm/sx/adapter-sx.sx",
     "shared/static/wasm/sx/adapter-dom.sx",
-    "shared/static/wasm/sx/cssx.sx",
     "shared/static/wasm/sx/boot-helpers.sx",
     "shared/static/wasm/sx/hypersx.sx",
     "shared/static/wasm/sx/engine.sx",