chore(deps): update dependency terser to v1.1.20

Author: renovate[bot]

Gemfile.lock

@@ -440,7 +440,7 @@ GEM
     sshkit-interactive (0.3.0)
       sshkit (~> 1.12)
     temple (0.8.2)
-    terser (1.1.17)
+    terser (1.1.20)
       execjs (>= 0.3.0, < 3)
     thor (1.2.2)
     thread_safe (0.3.6)