doc: Remove remark elements

They were not rendered with DSSSL, but now they show up by default using
XSLT.  Just remove them, since they are not useful.

doc/src/sgml/dml.sgml

@@ -3,10 +3,6 @@
 <chapter id="dml">
  <title>Data Manipulation</title>
 
- <remark>
-  This chapter is still quite incomplete.
- </remark>
-
  <para>
   The previous chapter discussed how to create tables and other
   structures to hold your data.  Now it is time to fill the tables

doc/src/sgml/ecpg.sgml

@@ -3592,7 +3592,7 @@ void PGTYPESdecimal_free(decimal *var);
 EXEC SQL ALLOCATE DESCRIPTOR <replaceable>identifier</replaceable>;
 </programlisting>
     The identifier serves as the <quote>variable name</quote> of the
-    descriptor area.  <remark>The scope of the allocated descriptor is WHAT?.</remark>
+    descriptor area.  <!-- The scope of the allocated descriptor is WHAT?. -->
     When you don't need the descriptor anymore, you should deallocate
     it:
 <programlisting>