fix: legend text.lineHeight option not work

[ssthouse]

fix the Echart's issue:
apache/echarts#15165
apache/echarts#15077

---

with the following config:

        legend: {
            left: 'center',
            top: 'center',
            data:[
                'GoogleMaps','Facebook','Youtube','Google+','Weixin',
                'Twitter', 'Skype', 'Messenger', 'Whatsapp', 'Instagram'
            ],
            textStyle: {
                lineHeight: 100,
            },
        },

Before fixed, legend.textStyle.lineHeight is not working.

After fixed: