Bump terser from 1.1.17 to 1.1.18

Bumps [terser](https://github.com/ahorek/terser-ruby) from 1.1.17 to 1.1.18.
- [Release notes](https://github.com/ahorek/terser-ruby/releases)
- [Changelog](https://github.com/ahorek/terser-ruby/blob/master/CHANGELOG.md)
- [Commits](ahorek/terser-ruby@1.1.17...1.1.18)

---
updated-dependencies:
- dependency-name: terser
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -310,7 +310,7 @@ GEM
       actionpack (>= 5.2)
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
-    terser (1.1.17)
+    terser (1.1.18)
       execjs (>= 0.3.0, < 3)
     thor (1.2.2)
     tilt (2.2.0)