file.xml: add the missing dot characters (#3532)

Author: mmalferov

reference/filesystem/functions/file.xml

@@ -62,7 +62,7 @@
          </term>
          <listitem>
           <simpara>
-           Omit newline at the end of each array element
+           Omit newline at the end of each array element.
           </simpara>
          </listitem>
         </varlistentry>
@@ -72,7 +72,7 @@
          </term>
          <listitem>
           <simpara>
-           Skip empty lines
+           Skip empty lines.
           </simpara>
          </listitem>
         </varlistentry>
@@ -82,7 +82,7 @@
          </term>
          <listitem>
           <simpara>
-           Don't use the default context
+           Don't use the default context.
           </simpara>
          </listitem>
         </varlistentry>