Bump terser and rollup-plugin-terser

Bumps [terser](https://github.com/terser/terser) to 5.15.1 and updates ancestor dependency [rollup-plugin-terser](https://github.com/TrySound/rollup-plugin-terser). These dependencies need to be updated together.


Updates `terser` from 3.17.0 to 5.15.1
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](terser/terser@v3.17.0...v5.15.1)

Updates `rollup-plugin-terser` from 4.0.4 to 7.0.2
- [Release notes](https://github.com/TrySound/rollup-plugin-terser/releases)
- [Commits](TrySound/rollup-plugin-terser@v4.0.4...v7.0.2)

---
updated-dependencies:
- dependency-name: terser
  dependency-type: indirect
- dependency-name: rollup-plugin-terser
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

package-lock.json

@@ -26,7 +26,7 @@
     "rollup-plugin-buble": "^0.19.6",
     "rollup-plugin-commonjs": "^10.0.0",
     "rollup-plugin-replace": "^2.2.0",
-    "rollup-plugin-terser": "^4.0.4",
+    "rollup-plugin-terser": "^7.0.2",
     "rollup-plugin-vue": "^6.0.0",
     "sass-loader": "^8.0.2",
     "vue": "^2.6.11",