Bump terser from 4.1.3 to 4.8.1 in /assets/packages/pjax (#2541)

Bumps [terser](https://github.com/terser/terser) from 4.1.3 to 4.8.1.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](terser/terser@v4.1.3...v4.8.1)

---
updated-dependencies:
- dependency-name: terser
  dependency-type: direct:development
...

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

assets/packages/pjax/package.json

@@ -11,6 +11,6 @@
       "build": "node ./build-tools/compile.js"
   },
   "devDependencies": {
-    "terser": "^4.1.3"
+    "terser": "^4.8.1"
   }
 }

assets/packages/pjax/yarn.lock

@@ -25,10 +25,10 @@ source-map@^0.6.0, source-map@~0.6.1:
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
   integrity sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==
 
-terser@^4.1.3:
-  version "4.1.3"
-  resolved "https://registry.yarnpkg.com/terser/-/terser-4.1.3.tgz#6074fbcf3517561c3272ea885f422c7a8c32d689"
-  integrity sha512-on13d+cnpn5bMouZu+J8tPYQecsdRJCJuxFJ+FVoPBoLJgk5bCBkp+Uen2hWyi0KIUm6eDarnlAlH+KgIx/PuQ==
+terser@^4.8.1:
+  version "4.8.1"
+  resolved "https://registry.yarnpkg.com/terser/-/terser-4.8.1.tgz#a00e5634562de2239fd404c649051bf6fc21144f"
+  integrity sha512-4GnLC0x667eJG0ewJTa6z/yXrbLGv80D9Ru6HIpCQmO+Q4PfEtBFi0ObSckqwL6VyQv/7ENJieXHo2ANmdQwgw==
   dependencies:
     commander "^2.20.0"
     source-map "~0.6.1"