find -type f -exec sh -c '[[ $(sed -n $= $0) -eq 2 ]]' {} ; -exec sed -i '1!d' {} +

for file in $(ls *.txt)
do
    LINENUMB=`wc -l $file | cut -f1 -d' '`
    if [[ $LINENUMB == 2 ]]; then
    sed -i '$d' $file
    fi
done