A few small fixes to server's README docs (#6428)

* Typo fix to server's README.md

Fix minor typo ("tonen") in server README.

* server readme grammar/style fixes.

Quickly went through this file to look for inconsistencies in
presentation of defaults, flag options, and looked for typos
and grammar issues.

Not perfect, but hopefully improved.

* Update README.md

Remove an extra space before newline.