notes doc: split up run-on sentences

notes doc: split up run-on sentences

When commit c4e2aa7d45 (notes.c: introduce "--[no-]stripspace" option,
2023-05-27) mentioned the new `--no-stripspace` in the documentation for
`-m` and `-F`, it created run-on sentences. It also used slightly
different language in the two sections for no apparent reason. Split the
sentences in two to improve readability, and while touching the two
sites, make them more similar.

Signed-off-by: Martin Ågren <redacted>
Signed-off-by: Junio C Hamano <redacted>