[docs] Update text.md

[lrgalego]

Remove inaccurate description.

Not sure if this was a limitation on a previous version. but calling this without a callback function just worked in the tutorial page

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[jhubbardsf]

I believe the arrow syntax is only required if the function takes a parameter that has to be specified (not the event). So if you had

<script>
let count = 0;

const add = (x) => {
    count += x;
}
</script>

<button on:click={add(1)}>
add one
</button>

The above would cause an unintended issue. The add function would be called on page load and count would equal 1 before the user ever clicked on button. This could be confusing for some. Changing button to

<button on:click={() => add(1)}>

would fix the issue and count will be 0 until the user clicks the button. So in the example you modified, you're right, it isn't necessarily needed. But it doesn't hurt anything either. There are cases where the arrow syntax is necessary.

Edit: I didn't notice that function focus() was a classic function. So in fact by changing () => field.focus() to field.focus it does have one subtle difference. You're implicitly passing the event to the focus function in the second case. You can check that by checking console.log(arguments) in the function. Where as () => field.focus() explicitly doesn't pass anything. Again, doesn't actually hurt anything or change anything, but small difference. And we implicitly pass event all the time. I'd agree with you it's not necessary to use the arrows syntax here.

[Conduitry]

There's been another PR a while ago that made this same change and that we didn't merge, but I don't fully remember what the reasoning was then.

[bluwy]

Yeah it's a duplicate of #6852 with explanation there. Closing as this as so.