[Validator] Update "suggest" section in composer.json.

Author: derrabus

composer.json

@@ -49,9 +49,9 @@
         "symfony/yaml": "<3.4"
     },
     "suggest": {
-        "psr/cache-implementation": "For using the metadata cache.",
+        "psr/cache-implementation": "For using the mapping cache.",
         "doctrine/annotations": "For using the annotation mapping. You will also need doctrine/cache.",
-        "doctrine/cache": "For using the default cached annotation reader and metadata cache.",
+        "doctrine/cache": "For using the default cached annotation reader.",
         "symfony/http-foundation": "",
         "symfony/intl": "",
         "symfony/translation": "For translating validation errors.",