Upgraded migration lint warnings to errors

- we have these rules in place to force the developer to think about the
  performance impact of their code
- unless they are enforced, it's easy for them to slip by and miss them
- this commit changes the warnings to errors, which will fail CI
- developers still have the ability to disable lines that flag the
  linting in case there is a valid use-case

.eslintrc.js

@@ -36,7 +36,7 @@ module.exports = {
         {
             files: 'core/server/data/migrations/versions/**',
             rules: {
-                'no-restricted-syntax': ['warn', {
+                'no-restricted-syntax': ['error', {
                     selector: 'ForStatement',
                     message: 'For statements can perform badly in migrations'
                 }, {