zramctl: update page

[Barry1]

The last example call (zramctl) needs also sudo.

• [ ] The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• [ ] The page(s) have at most 8 examples.
• [ ] The page description(s) have links to documentation or a homepage.
• [ ] The page(s) follow the content guidelines.
• [ ] The PR title conforms to the recommended templates.
• Version of the command being documented (if known):

[CLAassistant]

All committers have signed the CLA.