Fix

Author: mcmorisi

source/reference/driver-compatibility.txt

@@ -341,6 +341,24 @@ for that Ruby version is deprecated.
      - JRuby 9.2
      - JRuby 9.1
 
+   * - 2.21
+     - |checkmark|
+     - |checkmark|
+     - |checkmark|
+     - D
+     -
+     -
+     -
+     -
+     -
+     -
+     -
+     -
+     - |checkmark|
+     - |checkmark|
+     - D
+     -
+
    * - 2.20
      - |checkmark|
      - |checkmark|