doc/radosgw: Small improvements in s3_objects_dedup.rst

doc/radosgw: Small improvements in s3_objects_dedup.rst

Fix sentence that had "different same" to just "different" (verified the
right one from the original author).

Remove colon at the end of section titles.

Remove rendered horizontal lines between sections.

Use double backticks for command name.

Use regular apostrophe in one sentence to be consistent with the rest.

Add missing full stop at the end of several sentences.

Very small language improvements in a few sentences.

Use consistent indent in one line.

Remove hyphens from many word pairs and don't capitalize few terms.
For consistency with rest of the docs.

Fix typos "spliting" to "splitting", "underlined" to "underlying".

Spell out "thousands" instead of using an apostrophe after the number.

Reformat table to use row separators like rest of the docs instead of
empty columns.
Separate number and unit with a space. Remove rendered underscores that
seemed to be an attempt to imprecisely align cell contents to right.

Signed-off-by: Ville Ojamo <14869000+bluikko@users.noreply.github.com>