doc/radosgw: Small fixes and improvements in notifications.rst, part 2

doc/radosgw: Small fixes and improvements in notifications.rst, part 2

Use double backticks for data like configuration parameters.

Break very long lines around standard line length.

Don't list same parameter "user/password" in multiple list items,
instead just list all concerns under the same list item.

Add missing empty line before child unordered list.

Expand "args" in text to "arguments".

Start sentences with capital case and end in full stop consistently.

Remove indent from one whole unordered list that shouldn't be indented
(probably a copy-paste from a sub-list).
Indent lists inside notes with same amount of spaces everywhere.

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