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/systemd-run.xml

@@ -647,7 +647,7 @@ There is a screen on:
 
       <programlisting>$ systemd-run -t echo "&lt;${INVOCATION_ID}>" '&lt;${INVOCATION_ID}>'
       &lt;> &lt;5d0149bfa2c34b79bccb13074001eb20>
-      </programlisting>
+</programlisting>
 
       <para>The first argument is expanded by the shell (double quotes), but the second one is not expanded
       by the shell (single quotes).
@@ -673,7 +673,7 @@ There is a screen on:
       <programlisting>$ systemd-run --expand-environment=no -t bash \
       -c 'echo $SHELL $$ >/dev/stdout'
 /bin/bash 12345
-      </programlisting>
+</programlisting>
 
       <para>The last argument is passed verbatim to the
       <citerefentry project='man-pages'><refentrytitle>bash</refentrytitle><manvolnum>1</manvolnum></citerefentry>