Update README to match version support in MongoDB 8.0 (#5265)

Co-authored-by: shields <[email protected]>

Author: johnnyshields

README.md

@@ -19,9 +19,9 @@ Compatibility
 
 Mongoid supports and is tested against:
 
-- MRI 2.5-3.0
+- MRI 2.5 - 3.1
 - JRuby 9.2
-- MongoDB server 2.6-4.4
+- MongoDB server 3.6 - 5.0
 
 Issues
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