fix(derived): only the delete marker is a reserved name

A table's metadata columns are named per table - VAR_TXFROM, VAR_TXTO and
VAR_PROCESSED in MPE_TABLES hold those names, and they can be anything (the
bitemporal demo table uses VER_FROM_DTTM and VER_TO_DTTM).  When they exist
they are physical columns of the target, so the engine's collision check
already refuses a VAR_NM that matches one, whatever it is called.

The hard-coded list treated three example names as special: it refused them on
tables that use other names, and told the reader something untrue about what
is reserved.

sas/sasjs/macros/mpe_derived.sas

@@ -80,9 +80,10 @@
 
 %local reserved;
 
-/* the metadata columns of every Data Controller table */
-%let reserved=%str(_____DELETE__THIS__RECORD_____ TX_FROM TX_TO PROCESSED_DTTM
-  VAR_TXFROM VAR_TXTO VAR_PROCESSED);
+/* the only name that has to be refused outright - the metadata columns of the
+  target table are physical columns, so the engine's collision check covers
+  them whatever MPE_TABLES calls them */
+%let reserved=%str(_____DELETE__THIS__RECORD_____);
 
 %mp_abort(iftrue= (%length(&libds)=0 or %length(&dclib)=0)
   ,mac=&sysmacroname

sas/sasjs/services/hooks/mpe_derived_postedit.sas

@@ -111,8 +111,7 @@ data work.derived_check;
     then reason='VAR_NM must be a valid SAS name';
   else if verify(substr(var_nm,1,1),'0123456789')=0
     then reason='VAR_NM must not start with a digit';
-  else if var_nm in ('_____DELETE__THIS__RECORD_____','TX_FROM','TX_TO'
-    ,'PROCESSED_DTTM','VAR_TXFROM','VAR_TXTO','VAR_PROCESSED')
+  else if var_nm='_____DELETE__THIS__RECORD_____'
     then reason='VAR_NM is reserved';
   else if var_type not in ('C','N')
     then reason='VAR_TYPE must be C or N';