Fix each block tutorial wording (sveltejs#402)

* Improved wording.

The wording provided initially is confusing, and I believe is mistaken.

* Apply suggestions from code review

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Co-authored-by: Geoff Rich <[email protected]>

Author: faetalize

content/tutorial/01-svelte/04-logic/05-keyed-each-blocks/README.md

@@ -4,7 +4,7 @@ title: Keyed each blocks
 
 By default, when you modify the value of an `each` block, it will add and remove items at the _end_ of the block, and update any values that have changed. That might not be what you want.
 
-It's easier to show why than to explain. Click the 'Remove first thing' button a few times, and notice what happens: It removes the first `<Thing>` component, but the _last_ DOM node. Then it updates the `name` value in the remaining DOM nodes, but not the emoji, which in `Thing.svelte` is fixed when the component is created.
+It's easier to show why than to explain. Click the 'Remove first thing' button a few times, and notice what happens: it does not remove the first `<Thing>` component, but rather the _last_ DOM node. Then it updates the `name` value in the remaining DOM nodes, but not the emoji, which is fixed when each `<Thing>` is created.
 
 Instead, we'd like to remove only the first `<Thing>` component and its DOM node, and leave the others unaffected.