luci-app-watchcat: revert unnecessary quoting in init script

luci-app-watchcat: revert unnecessary quoting in init script

The quoting added in r18 for pinghosts is not needed. Multi-host support
remains fully functional, but the extra quotes caused inconsistent argument
handling between /etc/init.d/watchcat and /usr/bin/watchcat.sh,
especially for single-IP configurations.

This revert removes the unnecessary quoting in the init script and LUCI,
restoring consistent behavior while keeping multiple ping hosts supported.

Fixes: #28100 (watchcat: error if only one address is specified in pinghosts)
Signed-off-by: Ivan Diaz <redacted>