docs: Simplify certificate generation command.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@1838 44740490-163a-0410-bde0-09ae8108e29a

docs/simplesamlphp-idp.txt

@@ -159,16 +159,13 @@ Creating a SSL self signed certificate
 For test purposes, you can skip this section, and use the certificate
 included in the simpleSAMLphp distribution.
 
-Here is an example of `openssl`-commands which can be used to generate
+Here is an example of an `openssl`-command which can be used to generate
 a new private key key and the corresponding self-signed certificate.
 This key and certificate can be used to sign SAML messages:
 
-    openssl genrsa -out example.org.pem 1024
-    openssl req -new -key example.org.pem -out example.org.csr
-    openssl x509 -req -days 9999 -in example.org.csr -signkey example.org.pem -out example.org.crt
-    rm example.org.csr
+    openssl req -new -x509 -days 3652 -nodes -out example.org.crt -keyout example.org.pem
 
-The certificate above will be valid for 9999 days.
+The certificate above will be valid for 10 years.
 
 
 ### Note ###