Bump uglifier from 4.1.18 to 4.1.19 (forem#1030) [ci skip]

Bumps [uglifier](https://github.com/lautis/uglifier) from 4.1.18 to 4.1.19.
- [Release notes](https://github.com/lautis/uglifier/releases)
- [Changelog](https://github.com/lautis/uglifier/blob/master/CHANGELOG.md)
- [Commits](lautis/uglifier@v4.1.18...v4.1.19)

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

Gemfile.lock

@@ -864,7 +864,7 @@ GEM
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
     uber (0.1.0)
-    uglifier (4.1.18)
+    uglifier (4.1.19)
       execjs (>= 0.3.0, < 3)
     unf (0.1.4)
       unf_ext