(AzureCXP) fixes MicrosoftDocs/azure-docs#44118

Replace public.crt to contoso.crt

Author: SubhashVasarapu-MSFT

articles/application-gateway/self-signed-certificates.md

@@ -101,7 +101,7 @@ The CSR is a public key that is given to a CA when requesting a certificate. The
 1. Use the following command to create the certificate:
 
    ```
-   openssl x509 -req -in fabrikam.csr -CA public.crt -CAkey contoso.key -CAcreateserial -out fabrikam.crt -days 365 -sha256
+   openssl x509 -req -in fabrikam.csr -CA  contoso.crt -CAkey contoso.key -CAcreateserial -out fabrikam.crt -days 365 -sha256
    ```
 ### Verify the newly created certificate