Bump terser from 4.6.7 to 4.8.1 in /plugins/form

Bumps [terser](https://github.com/terser/terser) from 4.6.7 to 4.8.1.
- [Release notes](https://github.com/terser/terser/releases)
- [Changelog](https://github.com/terser/terser/blob/master/CHANGELOG.md)
- [Commits](https://github.com/terser/terser/commits)

---
updated-dependencies:
- dependency-name: terser
  dependency-type: indirect
...

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

plugins/form/yarn.lock

@@ -1613,9 +1613,9 @@ buffer-equal@^1.0.0:
   integrity sha1-WWFrSYME1Var1GaWayLu2j7KX74=
 
 buffer-from@^1.0.0:
-  version "1.1.1"
-  resolved "https://registry.yarnpkg.com/buffer-from/-/buffer-from-1.1.1.tgz#32713bc028f75c02fdb710d7c7bcec1f2c6070ef"
-  integrity sha512-MQcXEUbCKtEo7bhqEs6560Hyd4XaovZlO/k9V3hjVUF/zwW7KBVdSK4gIt/bzwS9MbR5qob+F5jusZsb0YQK2A==
+  version "1.1.2"
+  resolved "https://registry.yarnpkg.com/buffer-from/-/buffer-from-1.1.2.tgz#2b146a6fd72e80b4f55d255f35ed59a3a9a41bd5"
+  integrity sha512-E+XQCRwSbaaiChtv6k6Dwgc+bx+Bs6vuKJHHl5kox/BaKbhiXzqQOwK4cO22yElGp2OCmjwVhT3HmxgyPGnJfQ==
 
 buffer-xor@^1.0.3:
   version "1.0.3"
@@ -6247,9 +6247,9 @@ source-map-resolve@^0.5.0, source-map-resolve@^0.5.2:
     urix "^0.1.0"
 
 source-map-support@~0.5.12:
-  version "0.5.16"
-  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.16.tgz#0ae069e7fe3ba7538c64c98515e35339eac5a042"
-  integrity sha512-efyLRJDr68D9hBBNIPWFjhpFzURh+KJykQwvMyW5UiZzYwoF6l4YMMDIJJEyFWxWCqfyxLzz6tSfUFR+kXXsVQ==
+  version "0.5.21"
+  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.21.tgz#04fe7c7f9e1ed2d662233c28cb2b35b9f63f6e4f"
+  integrity sha512-uBHU3L3czsIyYXKX88fdrGovxdSCoTGDRZ6SYXtSRxLZUzHg5P/66Ht6uoUlHu9EZod+inXhKo3qQgwXUT/y1w==
   dependencies:
     buffer-from "^1.0.0"
     source-map "^0.6.0"
@@ -6608,9 +6608,9 @@ terser-webpack-plugin@^1.4.3:
     worker-farm "^1.7.0"
 
 terser@^4.1.2:
-  version "4.6.7"
-  resolved "https://registry.yarnpkg.com/terser/-/terser-4.6.7.tgz#478d7f9394ec1907f0e488c5f6a6a9a2bad55e72"
-  integrity sha512-fmr7M1f7DBly5cX2+rFDvmGBAaaZyPrHYK4mMdHEDAdNTqXSZgSOfqsfGq2HqPGT/1V0foZZuCZFx8CHKgAk3g==
+  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"