[Doc] Fix netlify cache & sync doc without pr content (taichi-dev#5003)

Author: Justinterest

netlify.toml

@@ -1,5 +1,5 @@
 [build]
-  command = "git clone https://github.com/taichi-dev/docs.taichi.graphics.git; git clone https://github.com/taichi-dev/docstring-gen docsgen; export DOCSTRING_GEN_PATH=\"$(pwd)/docsgen\"; export TAICHI_PATH=\"$(pwd)/python/taichi\"; export TAICHI_MAIN=\"$(pwd)\"; export TAICHI_WEBSITE=\"$(pwd)/docs.taichi.graphics\"; pip install sphinx-autoapi==1.8.4 gitpython pydata-sphinx-theme==0.7.2; cd $DOCSTRING_GEN_PATH/experimental; export current_version=master; make clean; make version; make apideploy; cd $TAICHI_WEBSITE/website; npm install --global [email protected]; yarn install; ./sync_docs.sh dev; yarn build;"
+  command = "git clone https://github.com/taichi-dev/docs.taichi.graphics.git; git clone https://github.com/taichi-dev/docstring-gen docsgen; export DOCSTRING_GEN_PATH=\"$(pwd)/docsgen\"; export TAICHI_PATH=\"$(pwd)/python/taichi\"; export TAICHI_MAIN=\"$(pwd)\"; export TAICHI_WEBSITE=\"$(pwd)/docs.taichi.graphics\"; pip install sphinx-autoapi==1.8.4 gitpython pydata-sphinx-theme==0.7.2; cd $DOCSTRING_GEN_PATH/experimental; export current_version=master; make clean; make version; make apideploy; cd $TAICHI_WEBSITE/website; git fetch origin master; git reset --hard origin/master; npm install --global [email protected]; yarn install; ./sync_version.sh; yarn build;"
 
   publish = "docs.taichi.graphics/website/build"
   # Cancel the build if there're no changes detected in docs/ folder.