backfill: document acceptance of revision-range in more standard manner
302aff09223f (backfill: accept revision arguments, 2026-03-26) added support for passing revision arguments to 'git backfill' but documented them only with a prose sentence: You may also specify the commit limiting options from git-rev-list(1). No other command that accepts revision arguments documents them this way. Commands like log, shortlog, and replay define a formal <revision-range> entry and include rev-list-options.adoc. Commands like bundle, fast-export, and filter-branch, which pass arguments through to the revision machinery without including the full options file, still define a formal <git-rev-list-args> entry explaining what is accepted. Add a formal <revision-range> entry in the synopsis and OPTIONS section, following the convention used by other commands, and mention that commit-limiting options from git-rev-list(1) are also accepted. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>