doc/apt.8.xml: fix typo, thanks to Jakub Wilk

Closes: #756056

doc/apt.8.xml

@@ -105,8 +105,8 @@
      <listitem><para><literal>upgrade</literal> is used to install the
      newest versions of all packages currently installed on the system
      from the sources enumerated in
-     <filename>/etc/apt/sources.list</filename>. New package will be
-     installed, but existing package will never removed.
+     <filename>/etc/apt/sources.list</filename>. New packages will be
+     installed, but existing packages will never be removed.
      </para></listitem>
      </varlistentry>