Update update.sh

Move sphinx to requirements.txt

Author: cocoatomo

Diff for: scripts/update.sh

@@ -4,9 +4,6 @@
 [ -n "$GITHUB_ACTIONS" ] && set -x
 set -e
 
-# Update Sphinx
-python -m pip install --upgrade sphinx
-
 # Allow language being passed as 1st argument, defaults to ja
 LANGUAGE=${1:-ja}