Add 'sa' to the list of the forbidden admin username

Author: eladtpro

articles/mysql/flexible-server/quickstart-create-server-portal.md

@@ -53,7 +53,7 @@ Complete these steps to create a flexible server:
     High Availability| Unchecked | For production servers, choose between [zone redundant high availability](concepts-high-availability.md#zone-redundant-ha-architecture) and [same-zone high availability](concepts-high-availability.md#same-zone-ha-architecture). This is highly recommended for business continuity and protection against VM failures|
     |Standby availability zone| No preference| Choose the standby server zone location and colocate it with the application standby server in case of zone failure |
     MySQL version|**5.7**| A MySQL major version.|
-    Admin username |**mydemouser**| Your own sign-in account to use when you connect to the server. The admin user name can't be **azure_superuser**, **admin**, **administrator**, **root**, **guest**, or **public**.|
+    Admin username |**mydemouser**| Your own sign-in account to use when you connect to the server. The admin user name can't be **azure_superuser**, **admin**, **administrator**, **root**, **guest**, **sa**, or **public**.|
     Password |Your password| A new password for the server admin account. It must contain between 8 and 128 characters. It must also contain characters from three of the following categories: English uppercase letters, English lowercase letters, numbers (0 through 9), and non-alphanumeric characters (!, $, #, %, and so on).|
     Compute + storage | **Burstable**, **Standard_B1ms**, **10 GiB**, **100 iops**, **7 days** | The compute, storage, IOPS, and backup configurations for your new server. Select **Configure server**. **Burstable**, **Standard_B1ms**, **10 GiB**, **100 iops**, and **7 days** are the default values for **Compute tier**, **Compute size**, **Storage size**, **iops**, and backup **Retention period**. You can leave those values as is or adjust them. For faster data loads during migration, it is recommended to increase the IOPS to the maximum size supported by compute size and later scale it back to save cost. To save the compute and storage selection, select **Save** to continue with the configuration. The following screenshot shows the compute and storage options.|