chore: update deprecated mitmproxy syntax
Fix for:
```
usage: mitmdump [options] [filter]
# mitmdump: error: unrecognized arguments: --replace
#
# --replace is deprecated.
# Please use  instead.
```
See also:
@@ -33,7 +33,7 @@ setup() {
# shellcheck disable=SC2094
cat <<<"$(jq '.networks.local.bind="127.0.0.1:'"$MITM_PORT"'"' dfx.json)" >dfx.json
- mitmdump -p "$MITM_PORT" --mode "reverse:http://$BACKEND" --replace '/~s/Hello,/Hullo,' &
+ mitmdump -p "$MITM_PORT" --mode "reverse:http://$BACKEND" --replacements '/~s/Hello,/Hullo,' &
MITMDUMP_PID=$!
timeout 5 sh -c \
