Docs: Add database update for Discounts in v4.6.22

Author: mnocon

docs/update_and_migration/from_4.6/update_from_4.6.22.md

@@ -0,0 +1 @@
+No additional steps needed.

docs/update_and_migration/from_4.6/update_from_4.6.md

@@ -395,6 +395,26 @@ To use the [latest features](ibexa_dxp_v4.6.md) added to them, update them separ
 
     Then apply manually the changes described below.
 
+    ## 4.6.22
+
+    ### Database update
+
+    Run the following scripts:
+
+    === "MySQL"
+
+        ``` sql
+        alter table ibexa_discount add override_prioritization tinyint(1) not null default 0;
+        create index ibexa_discount_prioritization_idx on ibexa_discount (override_prioritization, type, priority);
+        ```
+
+    === "PostgreSQL"
+
+        ``` sql
+        alter table ibexa_discount add override_prioritization boolean not null default false;
+        create index ibexa_discount_prioritization_idx on ibexa_discount (override_prioritization, type, priority);
+        ```
+
     ## 4.6.20
 
     ### Policy changes