rev-list-options: fix off-by-one in '--filter=blob:limit=<n>' explainer

rev-list-options: fix off-by-one in '--filter=blob:limit=<n>' explainer

'--filter=blob:limit=<n>' was introduced in 25ec7bcac0 (list-objects:
filter objects in traverse_commit_list, 2017-11-21) and later expanded
to bitmaps in 84243da129 (pack-bitmap: implement BLOB_LIMIT filtering,
2020-02-14)

The logic that was introduced in these commits (and that still persists
to this day) omits blobs larger than _or equal_ to n bytes or units.

However, the documentation (Documentation/rev-list-options.txt) states:

>The form '--filter=blob:limit=<n>[kmg]' omits blobs larger than n
bytes or units. n may be zero.

Moreover, the t6113-rev-list-bitmap-filters.sh tests for exactly this
logic, so it seems it is the documentation that needs fixing, not the
code.

This changes the explanation to be similar to
Documentation/git-clone.txt, which is correct.

Signed-off-by: Nikolay Edigaryev <edigaryev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>