Drop obsolete experimentalDecorators #11918

Because we don't use parameter decorators anymore, so we don't need it.

Author: PowerKiKi

tsconfig.json

@@ -12,7 +12,6 @@
         "isolatedModules": true,
         "sourceMap": true,
         "declaration": false,
-        "experimentalDecorators": true,
         "importHelpers": true,
         "strictNullChecks": true,
         "target": "ES2022",