fix: get rid of ++ operator in ref example

[jacekkarczmarczyk]

Description of Problem

Example showing ref's value update uses ++ operator, I think that assigning new value is more common and personally i think that using ++ operator should be avoided in this kind of examples (unless you want to show that you can use this specific operator in some specific cases)

Proposed Solution

- count.value++
+ count.value = 1

Alternative solution

- count.value++
+ count.value = count.value + 1

Additional comments

There could be also example with objects, like

const data = ref(null)

data.value = { name: 'John Doe' }

Let me know if this should be added as well to this PR

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