Fixed the key of the example exlusion.

Author: camrein

doc/analyzers/PH_S019.md

@@ -17,5 +17,5 @@ The methods `AddAsync` and `AddRangeAsync` of entity framework's `DbSet` and `Db
 ```
 # A white-space separated list of methods to exclude when searching for async counterparts
 # Format: <type-specifier>:<method1>,<method2>
-dotnet_diagnostic.PH_P012.named = Microsoft.EntityFrameworkCore.DbContext:Add,AddRange Microsoft.EntityFrameworkCore.DbSet`1:Add,AddRange
+dotnet_diagnostic.PH_P019.exclusions = Microsoft.EntityFrameworkCore.DbContext:Add,AddRange Microsoft.EntityFrameworkCore.DbSet`1:Add,AddRange
 ```