numfmt: add Dutch translation and fix placeholders (#13156)

pages/common/numfmt.md

@@ -5,12 +5,12 @@
 
 - Convert 1.5K (SI Units) to 1500:
 
-`numfmt --from={{si}} {{1.5K}}`
+`numfmt --from=si 1.5K`
 
 - Convert 5th field (1-indexed) to IEC Units without converting header:
 
-`ls -l | numfmt --header={{1}} --field={{5}} --to={{iec}}`
+`ls -l | numfmt --header=1 --field=5 --to=iec`
 
 - Convert to IEC units, pad with 5 characters, left aligned:
 
-`du -s * | numfmt --to={{iec}} --format="{{%-5f}}"`
+`du -s * | numfmt --to=iec --format="%-5f"`