man: drop whitespace from final <programlisting> lines

In the troff output, this doesn't seem to make any difference. But in the
html output, the whitespace is sometimes preserved, creating an additional
gap before the following content. Drop it everywhere to avoid this.

man/org.freedesktop.machine1.xml

@@ -183,7 +183,7 @@ node /org/freedesktop/machine1 {
   interface org.freedesktop.DBus.Introspectable { ... };
   interface org.freedesktop.DBus.Properties { ... };
 };
-    </programlisting>
+</programlisting>
 
     <!--method UnregisterMachine is not documented!-->
 
@@ -531,7 +531,7 @@ node /org/freedesktop/machine1/machine/rawhide {
   interface org.freedesktop.DBus.Introspectable { ... };
   interface org.freedesktop.DBus.Properties { ... };
 };
-    </programlisting>
+</programlisting>
 
     <!--method GetUIDShift is not documented!-->
 
@@ -687,7 +687,7 @@ node /org/freedesktop/machine1/machine/rawhide {
 $ gdbus introspect --system \
   --dest org.freedesktop.machine1 \
   --object-path /org/freedesktop/machine1
-      </programlisting>
+</programlisting>
     </example>
 
     <example>
@@ -697,7 +697,7 @@ $ gdbus introspect --system \
 $ gdbus introspect --system \
   --dest org.freedesktop.machine1 \
   --object-path /org/freedesktop/machine1/machine/rawhide
-      </programlisting>
+</programlisting>
     </example>
   </refsect1>