Change "Version" to "Revision" in the document change history for consistency.

Signed-off-by: Bill Schmidt <wschmidt@linux.vnet.ibm.com>

specification/bk_main.xml

@@ -109,7 +109,7 @@
           <revdescription>
             <itemizedlist spacing="compact">
               <listitem>
-                <para>Version 1.3: POWER9 support.
+                <para>Revision 1.3: POWER9 support.
                 </para>
               </listitem>
             </itemizedlist>
@@ -120,7 +120,7 @@
           <revdescription>
             <itemizedlist spacing="compact">
               <listitem>
-                <para>Version 1.2: POWER8 errata.
+                <para>Revision 1.2: POWER8 errata.
                 </para>
               </listitem>
             </itemizedlist>
@@ -131,7 +131,7 @@
           <revdescription>
             <itemizedlist spacing="compact">
               <listitem>
-                <para>Version 1.1: Incorporate errata.</para>
+                <para>Revision 1.1: Incorporate errata.</para>
               </listitem>
             </itemizedlist>
           </revdescription>
@@ -141,7 +141,7 @@
           <revdescription>
             <itemizedlist spacing="compact">
               <listitem>
-                <para>Version 1.0 initial release.</para>
+                <para>Revision 1.0: Initial release.</para>
               </listitem>
             </itemizedlist>
           </revdescription>