Update ejs to v3.1.7 (or latest)

[lorezyra]

Need to update ejs (https://github.com/mde/ejs) dependency due to critical vulnerabilities.

hexo-generator-seo-friendly-sitemap/package.json

Lines 16 to 23 in 106d086

	"dependencies": {
	"bluebird": "3.5.4",
	"ejs": "2.6.1",
	"lodash": "4.17.12",
	"moment": "2.24.0",
	"pretty-data": "0.40.0",
	"url-join": "4.0.0"
	},

Reference

• High severity vulnerability that affects ejs
• High severity vulnerability that affects ejs
• Moderate severity vulnerability that affects ejs