rename RC to pre-relesae

Author: oranagra

downloads.json

@@ -5,7 +5,7 @@
       "notes": "This is where all the development happens. Only for hard-core hackers. Use only if you need to test the latest features or performance improvements. This is going to be the next Redis release in a few months."
     },
 
-    "release-candidate": {
+    "pre-release": {
       "branch": "6.2",
       "version": "6.2-rc1",
       "notes": "Redis 6.2 includes many new commands and improvements, but no big features. It mainly makes Redis more complete and addresses issues that have been requested by many users frequently or for a long time."