docs: use a fixed commit of lv_web_emscripten

fixes #4071

scripts/build_html_examples.sh

@@ -4,6 +4,7 @@ export PATH="/usr/lib/ccache:/usr/local/opt/ccache/libexec:$PATH"
 CURRENT_REF="$(git rev-parse HEAD)"
 rm -rf emscripten_builder
 git clone https://github.com/lvgl/lv_sim_emscripten.git emscripten_builder
+git checkout 45e0bc5c8d3e55cfbcaf8214361d2335b8b9a7b4
 scripts/genexamplelist.sh > emscripten_builder/examplelist.c
 cd emscripten_builder
 git submodule update --init -- lvgl