fix(ci): silence TS 6 deprecation for downlevelIteration

Cypress 14.5.4's webpack-preprocessor injects `downlevelIteration: true`
into its internal ts-loader config. TS 6 errors on it as deprecated and
blocks spec compilation. Set `ignoreDeprecations: "6.0"` at the root so
the cypress tsconfig inherits it and the deprecation downgrades to a
silent acceptance until TS 7.

Author: antfu

tsconfig.json

@@ -28,6 +28,7 @@
     "noEmit": true,
     "esModuleInterop": true,
     "forceConsistentCasingInFileNames": true,
+    "ignoreDeprecations": "6.0",
     "skipLibCheck": true
   },
   "include": [