Prow: increase max Azure CI clusters to 20

We now have 1000vCPUs, so let's bump cluster size back up to
accommodate Azure CI jobs.

Signed-off-by: Yu Qi Zhang <[email protected]>

Author: yuqi-zhang

core-services/prow/02_config/_boskos.yaml

@@ -6,8 +6,8 @@ resources:
   max-count:  120
 - type: azure4-quota-slice
   state: free
-  min-count: 5
-  max-count: 5
+  min-count: 20
+  max-count: 20
 - type: gcp-quota-slice
   state: free
   min-count: 1000