Change gitlab/log permissions in installation.md

This patch changes default permission of the gitlab/log directory to
u+rwX,go-w. This is done to make the directory NOT readable by group and
others and to avoid logrotate complaining about it. chmod 755 is not
used to avoid setting executable bit on file within the log dir.

doc/install/installation.md

@@ -159,7 +159,7 @@ We recommend using a PostgreSQL database. For MySQL check [MySQL setup guide](da
     # Make sure GitLab can write to the log/ and tmp/ directories
     sudo chown -R git log/
     sudo chown -R git tmp/
-    sudo chmod -R u+rwX log/
+    sudo chmod -R u+rwX,go-w log/
     sudo chmod -R u+rwX tmp/
 
     # Create directory for satellites