Fix locale string configuration for parentoptions

The `parentoptions` heading is missing from the locale string
file. The result is that in the command reference pages, the
second table has no heading. It is weird to see two tables on
the same page without this heading text.

Author: tengqm

Diff for: i18n/en/en.toml

@@ -456,6 +456,9 @@ other = "This article is more than one year old. Older articles may contain outd
 [page_deprecated]
 other = "(stale page)"
 
+[parentoptions_heading]
+other = "Parent Options Inherited"
+
 [patch_release]
 other = "Patch Release"