[doc] use sudo for all apt commands

docs/installation/index.rst

@@ -105,8 +105,8 @@ Ensure you have a recent version of nginx on your server. On Debian-like system,
 
 .. code-block:: bash
 
-    apt-get update
-    apt-get install nginx
+    sudo apt-get update
+    sudo apt-get install nginx
 
 Then, download our sample virtualhost file and proxy conf:
 
@@ -132,7 +132,7 @@ Apache2
 Ensure you have a recent version of apache2 installed on your server.
 You'll also need the following dependencies::
 
-   apt install libapache2-mod-xsendfile
+   sudo apt-get install libapache2-mod-xsendfile
 
 Then, download our sample virtualhost file: