doc/radosgw: Small fixes and improvements in notifications.rst, part 1

doc/radosgw: Small fixes and improvements in notifications.rst, part 1

Fix ordering of list items so that the sub-list is after the parent list
item referring to it.
Also fix multiple formatting errors in the same unordered list.

Fix unordered list rendered as a single sentence due to missing empty
line.

Break many long lines around standard line length.

Don't use hyphen for "regular expressions".

Use double backticks for data like configuration parameters.

Fix double space in an example CLI command.

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

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

Trim section title formatting syntax to text length.

Capitalize "URI" and "Kafka" consistently.

Use quotation marks in one occurrence of the value "true" instead of
single backticks for consistency.

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