SIVA-549 In docs update DigiDoc client reference

docs/siva3/structure_and_activities.md

@@ -80,7 +80,7 @@ Required:
 
 | Component | Description |
 |------------------------------|--------------------------------------------------------|
-| **Digidoc3 client** | DigiDoc4 client is a program that can be used to sign digitally with ID-card and Mobile-ID, check the validity of digital signatures and open and save documents inside the signature container. See the github [project](https://github.com/open-eid/DigiDoc4-Client) for further details. |
+| **DigiDoc4 client** | DigiDoc4 client is a program that can be used to sign digitally with ID-card and Mobile-ID, check the validity of digital signatures and open and save documents inside the signature container. See the github [project](https://github.com/open-eid/DigiDoc4-Client) for further details. |
 | **XROAD security server** | A client subsystem that, once connected, allows SiVa to be integrated into the [X-Road data exchange layer](https://www.ria.ee/en/state-information-system/data-exchange-platforms/data-exchange-layer-x-tee)                                                                     |
 | **EU TSL provider** | A subsystem that provides SiVa with a current TSL. An HTTPS endpoint, that provides an XML formatted file that lists all trusted service providers along with their certificates.                                                                                                 |
 | **Monitoring** | (Optional) A subsystem that tracks the health and uptime of SiVa webapps</li></ul>                                                                                                                                                                                                |