Fixes to the documentation of the "cloud write" feature

[darkstar]

This PR fixes several issues with the "cloud write" documentation.

• The volume modify command does not take the -aggregate option. This is likely a copy/paste error from the volume create command further up.
• Both the volume create and volume modify commands require specifying an SVM name. Added -vserver vs1 as with other documents everywhere
• Fixed copy/paste issues in worgin in the paragraphs above the volume modify commands which were also referencing the Aggregate
• Changed the generic parameter description -is-cloud-write-enabled <true|false> to either specify true or false directly in the commands that are supposed to enable/disable the feature. The generic command line in the "create volume" section should be left as-is

Also, in a second commit (to make it easier to drop/ignore those changes), all uses of the phrase "cloud write" vs "cloud-write" were unified to the one without hypen/dash, as suggested by the manual pages. If this is not desired (or if the term "cloud-write" should be used instead) let me know then I can change that

The one line change in the last line is some newline-at-eof issue that I was sadly not able to get rid of...

[darkstar]

If you prefer, for the future I can also open an issue and link the PR to that if that's easier for you to work with?