Update TodoMVC demo (#23911)
Update TodoMVC demo (#23911)

Add `sandbox="allow-forms"` to `<amp-script>`
lannka/amphtml,adup-tech/amphtml,yandex-pcode/amphtml,lannka/amphtml,adup-tech/amphtml,honeybadgerdontcare/amphtml,Gregable/amphtml,adup-tech/amphtml,ampproject/amphtml,cory-work/amphtml,lannka/amphtml,mhc-gh/amphtml,jridgewell/amphtml,smartadserver/amphtml,honeybadgerdontcare/amphtml,honeybadgerdontcare/amphtml,ampproject/amphtml,tlong2/amphtml,mhc-gh/amphtml,Gregable/amphtml,sharethrough/amphtml,yandex-pcode/amphtml,nexxtv/amphtml,jpettitt/amphtml,cory-work/amphtml,jpettitt/amphtml,rsimha-amp/amphtml,dotandads/amphtml,zhouyx/amphtml,danielrozenberg/amphtml,jpettitt/amphtml,taboola/amphtml,erwinmombay/amphtml,smartadserver/amphtml,adup-tech/amphtml,dotandads/amphtml,mhc-gh/amphtml,mhc-gh/amphtml,rsimha-amp/amphtml,dotandads/amphtml,src-code/amphtml,ampproject/amphtml,danielrozenberg/amphtml,danielrozenberg/amphtml,Gregable/amphtml,media-net/amphtml,adup-tech/amphtml,erwinmombay/amphtml,tlong2/amphtml,yandex-pcode/amphtml,ampproject/amphtml,src-code/amphtml,cory-work/amphtml,smartadserver/amphtml,prateekbh/amphtml,taboola/amphtml,zhangsu/amphtml,mhc-gh/amphtml,jmadler/amphtml,alanorozco/amphtml,zhangsu/amphtml,jmadler/amphtml,jridgewell/amphtml,jridgewell/amphtml,alanorozco/amphtml,zhangsu/amphtml,tlong2/amphtml,taboola/amphtml,nexxtv/amphtml,yandex-pcode/amphtml,adup-tech/amphtml,zhouyx/amphtml,jridgewell/amphtml,danielrozenberg/amphtml,Gregable/amphtml,jpettitt/amphtml,zhouyx/amphtml,lannka/amphtml,lannka/amphtml,voyagegroup/amphtml,taboola/amphtml,alanorozco/amphtml,zhangsu/amphtml,yandex-pcode/amphtml,erwinmombay/amphtml,src-code/amphtml,dotandads/amphtml,yandex-pcode/amphtml,jmadler/amphtml,prateekbh/amphtml,danielrozenberg/amphtml,voyagegroup/amphtml,cory-work/amphtml,alanorozco/amphtml,zhouyx/amphtml,cory-work/amphtml,ampproject/amphtml,Gregable/amphtml,zhouyx/amphtml,erwinmombay/amphtml,honeybadgerdontcare/amphtml,voyagegroup/amphtml,rsimha-amp/amphtml,honeybadgerdontcare/amphtml,Gregable/amphtml,zhouyx/amphtml,sharethrough/amphtml,alanorozco/amphtml,media-net/amphtml,sharethrough/amphtml,jridgewell/amphtml,sharethrough/amphtml,nexxtv/amphtml,alanorozco/amphtml,taboola/amphtml,danielrozenberg/amphtml,tlong2/amphtml,voyagegroup/amphtml,media-net/amphtml,src-code/amphtml,ampproject/amphtml,nexxtv/amphtml,danielrozenberg/amphtml,rsimha-amp/amphtml,ampproject/amphtml,media-net/amphtml,Gregable/amphtml,rsimha-amp/amphtml,jmadler/amphtml,lannka/amphtml,tlong2/amphtml,zhangsu/amphtml,jpettitt/amphtml,honeybadgerdontcare/amphtml,smartadserver/amphtml,src-code/amphtml,mhc-gh/amphtml,alanorozco/amphtml,voyagegroup/amphtml,prateekbh/amphtml,yandex-pcode/amphtml,jmadler/amphtml,danielrozenberg/amphtml,voyagegroup/amphtml,jmadler/amphtml,Gregable/amphtml,smartadserver/amphtml,erwinmombay/amphtml,zhouyx/amphtml,zhangsu/amphtml,media-net/amphtml,ampproject/amphtml,nexxtv/amphtml,honeybadgerdontcare/amphtml,prateekbh/amphtml,media-net/amphtml,voyagegroup/amphtml,taboola/amphtml,dotandads/amphtml,cory-work/amphtml,prateekbh/amphtml,jridgewell/amphtml,jridgewell/amphtml,rsimha-amp/amphtml,erwinmombay/amphtml,nexxtv/amphtml,prateekbh/amphtml,jpettitt/amphtml,sharethrough/amphtml,dotandads/amphtml,jpettitt/amphtml,alanorozco/amphtml,tlong2/amphtml,mhc-gh/amphtml,src-code/amphtml,taboola/amphtml,nexxtv/amphtml,smartadserver/amphtml,jpettitt/amphtml,rsimha-amp/amphtml,media-net/amphtml,cory-work/amphtml,lannka/amphtml,media-net/amphtml,mhc-gh/amphtml,prateekbh/amphtml,sharethrough/amphtml