grdfilter: Fix the long names for arguments of the -N option (#8842)

* grdfilter: Fix the long names for arguments of the -N option

* Fix a test

Author: seisman

src/longopt/grdfilter_inc.h

@@ -34,7 +34,7 @@ static struct GMT_KEYWORD_DICTIONARY module_kw[] = {
 	GMT_G_OUTGRID_KW,
 	GMT_I_INCREMENT_KW,
 	{ 0, 'N', "nans",
-	          "i,p,r",             "ignore,coregnan,anynan",
+	          "i,p,r",             "ignore,preserve,replace",
 	          "",                  "",
 		  GMT_TP_STANDARD },
 	{ 0, 'T', "toggle_registration|toggle",         "", "", "", "", GMT_TP_STANDARD },

test/grdfilter/grdfilter-l2s.sh

@@ -36,7 +36,7 @@ gmt $m $l2s --outgrid=/somefile=nf+divide:10+nan:-999+offset:6 >> $b
 gmt $m $l2s --outgrid=/otherfile+offset:a >> $b
 gmt $m $l2s --outgrid=/otherfile+scale:100+gdal >> $b
 gmt $m $l2s --increment=12+exact/15+number >> $b
-gmt $m $l2s --nans=ignore --nans=coregnan --nans=anynan >> $b
+gmt $m $l2s --nans=ignore --nans=preserve --nans=replace >> $b
 gmt $m $l2s --toggle_registration --toggle >> $b
 
 diff $a $b --strip-trailing-cr > fail