Bump version to 10.3 (final)

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
docs: Update 10.3 release notes

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
docs: Add 10.3 sha256 sums, news item and link release notes

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>