Feature: update versions to V4.2.1

Author: xhycode

Marlin/src/inc/Version.h

@@ -38,7 +38,7 @@
   /**
    * Marlin release version identifier
    */
-  #define SHORT_BUILD_VERSION "SM2-4.1.0"
+  #define SHORT_BUILD_VERSION "SM2-4.2.1"
 
   /**
    * Verbose version identifier which should contain a reference to the location
@@ -51,7 +51,7 @@
    * here we define this default string as the date where the latest release
    * version was tagged.
    */
-  #define STRING_DISTRIBUTION_DATE "2021-01-28"
+  #define STRING_DISTRIBUTION_DATE "2021-03-16"
 
   /**
    * Required minimum Configuration.h and Configuration_adv.h file versions.