PYTHON-4637 Fix azure kms task variant (mongodb#1779)

Author: blink1073

.evergreen/config.yml

@@ -3153,7 +3153,7 @@ buildvariants:
 
 - name: testazurekms-variant
   display_name: "Azure KMS"
-  run_on: rhel87-small
+  run_on: debian11-small
   tasks:
     - name: testazurekms_task_group
       batchtime: 20160 # Use a batchtime of 14 days as suggested by the CSFLE test README