man/systemd.mstack: use <varname> instead of <variable>

Otherwise, `<variable>location</variable>` is rendered:

```
[2365/2925] Generating man/systemd.mstack.7 with a custom command
Element variable in namespace '' encountered in para, but no template matches.
```

diff --git a/man/systemd.mstack.xml b/man/systemd.mstack.xml
index 03e41afcfecd28e32dd70711e32d02a38d6bc037..b0d6d5f5453475fd511859f7dc039be879d8cead 100644 (file)
--- a/man/systemd.mstack.xml
+++ b/man/systemd.mstack.xml
@@ -50,7 +50,7 @@
       they be missing.</para></listitem>
 
       <listitem><para>A <filename>bind@<replaceable>location</replaceable>/</filename> directory will be bind
-      mounted to the mount point indicated by the <variable>location</variable> identifier, in read-write
+      mounted to the mount point indicated by the <varname>location</varname> identifier, in read-write
       fashion. The location is encoded via the same escaping logic used for naming <literal>.mount</literal>
       units, i.e. slashes become dashes.</para></listitem>