fix: misleading foundMessage (#354)

Author: nopeless

lib/rules/prefer-message-ids.js

@@ -13,7 +13,7 @@ module.exports = {
     type: 'problem',
     docs: {
       description:
-        'require using `messageId` instead of `message` to report rule violations',
+        'require using `messageId` instead of `message` or `desc` to report rule violations',
       category: 'Rules',
       recommended: true,
       url: 'https://github.com/eslint-community/eslint-plugin-eslint-plugin/tree/HEAD/docs/rules/prefer-message-ids.md',
@@ -23,7 +23,8 @@ module.exports = {
     messages: {
       messagesMissing:
         '`meta.messages` must contain at least one violation message.',
-      foundMessage: 'Use `messageId` instead of `message`.',
+      foundMessage:
+        'Use `messageId` instead of `message` (for violations) or `desc` (for suggestions).',
     },
   },