[cron] Bump distribution date (2020-06-21)

Marlin/src/inc/Version.h

@@ -42,7 +42,7 @@
  * version was tagged.
  */
 #ifndef STRING_DISTRIBUTION_DATE
-  #define STRING_DISTRIBUTION_DATE "2020-06-20"
+  #define STRING_DISTRIBUTION_DATE "2020-06-21"
 #endif
 
 /**