Bump core-js from 3.38.1 to 3.39.0 in /vsts-variable-transform/v1

Bumps [core-js](https://github.com/zloirock/core-js/tree/HEAD/packages/core-js) from 3.38.1 to 3.39.0.
- [Release notes](https://github.com/zloirock/core-js/releases)
- [Changelog](https://github.com/zloirock/core-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/zloirock/core-js/commits/v3.39.0/packages/core-js)

---
updated-dependencies:
- dependency-name: core-js
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

vsts-variable-transform/v1/package-lock.json

@@ -8,7 +8,7 @@
   },
   "dependencies": {
     "azure-pipelines-task-lib": "^3.4.0",
-    "core-js": "^3.38.1"
+    "core-js": "^3.39.0"
   },
   "scripts": {
     "initdev:npm": "npm install",