Doc: networking: Fix various typos in rds.rst

Doc: networking: Fix various typos in rds.rst

Corrected "sages" to "messages" in the bitmap allocation description.
Fixed "competed" to "completed" in the recv path datagram handling section.
Corrected "privatee" to "private" in the multipath RDS section.
Fixed "mutlipath" to "multipath" in the transport capabilities description.

These changes improve documentation clarity and maintain consistency.

Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Link: https://patch.msgid.link/20250522074413.3634446-1-alok.a.tiwari@oracle.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>