build!: update library to use Node 12 (#333)

* feat!: Update library to use Node 12

* 🦉 Updates from OwlBot post-processor

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Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: 2 people

document-ai/package.json

@@ -4,7 +4,7 @@
   "license": "Apache-2.0",
   "author": "Google LLC",
   "engines": {
-    "node": ">= 10.17.0"
+    "node": ">=12.0.0"
   },
   "files": [
     "*.js"