update desc of CVE-2019-5420 to indiciate unaffected versions

Author: schoblaska

gems/railties/CVE-2019-5420.yml

@@ -13,7 +13,7 @@ description: |
   CVE-2019-5420.
 
   Versions Affected:  6.0.0.X, 5.2.X.
-  Not affected:       None.
+  Not affected:       < 5.2.0
   Fixed Versions:     6.0.0.beta3, 5.2.2.1
 
   Impact