build(docs-infra): disable cli.warnings.typescriptMismatch warnings (#27536)

cli is not yet officially compatible with typescript 3.2, so we need to disable the version check via:

ng config cli.warnings.typescriptMismatch false

PR Close #27536

aio/angular.json

@@ -2,7 +2,10 @@
   "$schema": "./node_modules/@angular-devkit/core/src/workspace/workspace-schema.json",
   "version": 1,
   "cli": {
-    "packageManager": "yarn"
+    "packageManager": "yarn",
+    "warnings": {
+      "typescriptMismatch": false
+    }
   },
   "newProjectRoot": "projects",
   "projects": {