man: tweak description of blockdev@.target

In particular, let's just say "is" and "must" instead of "may be" and
"should". The weaker forms are obviously correct, but the text is easier to
understand if non-conditional forms are used.

man/systemd.special.xml

@@ -803,20 +803,19 @@
     <variablelist>
       <varlistentry>
           <term><filename>blockdev@.target</filename></term>
-          <listitem><para>This template unit may be used to order mount units and other consumers of block
-          devices against services that synthesize these block devices. This is intended to be used to order
-          storage services (such as
+          <listitem><para>This template unit is used to order mount units and other consumers of block
+          devices after services that synthesize these block devices. In particular, this is intended to be
+          used with storage services (such as
           <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>)
-          that allocate and manage a virtual block device against mount units and other consumers of
-          it. Specifically, the storage services are supposed to be orderd before an instance of
-          <filename>blockdev@.target</filename>, and the mount unit (or other consuming unit, such as a swap
-          unit) after it. The ordering is particular relevant during shutdown, as it ensures that the mount
-          is deactivated first and the service backing the mount only deactivated after that completed. The
-          <filename>blockdev@.target</filename> instance should be pulled in via a <option>Wants=</option>
-          dependency of the storage daemon and thus generally not be part of any transaction unless a storage
-          daemon is used. The instance name for instances of this template unit is supposed to be the
-          properly escaped bock device node path, e.g. <filename>blockdev@dev-mapper-foobar.target</filename>
-          for a storage device <filename>/dev/mapper/foobar</filename>.</para></listitem>
+          that allocate and manage a virtual block device. Storage services are ordered before an instance of
+          <filename>blockdev@.target</filename>, and the consumer units after it. The ordering is
+          particularly relevant during shutdown, as it ensures that the mount is deactivated first and the
+          service backing the mount later. The <filename>blockdev@.target</filename> instance should be
+          pulled in via a <option>Wants=</option> dependency of the storage daemon and thus generally not be
+          part of any transaction unless a storage daemon is used. The instance name for instances of this
+          template unit must be a properly escaped block device node path, e.g.
+          <filename>blockdev@dev-mapper-foobar.target</filename> for the storage device
+          <filename>/dev/mapper/foobar</filename>.</para></listitem>
       </varlistentry>
       <varlistentry>
         <term><filename>cryptsetup-pre.target</filename></term>