Remove unused eslint rule !! (#208508)

## Summary

We created a new plugin for uptime code so this eslint rule is not valid
anymore and is not being used !!

.eslintrc.js

@@ -1019,21 +1019,6 @@ module.exports = {
         ],
       },
     },
-    {
-      // disable imports from legacy uptime plugin
-      files: [
-        'x-pack/solutions/observability/plugins/synthetics/public/apps/synthetics/**/*.{js,mjs,ts,tsx}',
-      ],
-      rules: {
-        'no-restricted-imports': [
-          'error',
-          {
-            patterns: ['**/legacy_uptime/*'],
-            paths: RESTRICTED_IMPORTS,
-          },
-        ],
-      },
-    },
     {
       files: [
         'x-pack/solutions/observability/plugins/apm/**/*.{js,mjs,ts,tsx}',