Disable/enable sync confudsed users who only use web

[ScharfViktor]

Precondition: user einstein uses only web client Steps:

• admin share folder f1 with content to user einstein
• einstein opens shares->f1 and can see folder content
• einstein disables sync -> he can still see folder content

Actual: For a user who uses only web client disable/enable sync looks like something that's not needed or doesn't work

Expected: provide to users some clues. @tbsbdr what do you think

@butonic please add your remarks CC @AlexAndBear