incorrect icon: Improve close / checkmark icon.

### Describe the Issue

Just a minor but somewhat annoying issue from a meticulous UI dev. Especially when using `close` and `checkmark` icon together. It seems that either the `close` is not correct or `checkmark`. You can decide.

### Comparison

| Type | Close | Checkmark | Compare | Comment |
| --- | :-: | :-: | :-: | --- |
| outline ||||Seems ok.|
| filled ||||The `close` appears too thick or the `checkmark` too thin.|
| sharp ||||Seems ok.|


We see that the `checkmark` outline and filled appear the same. The filled checkmark should be thicker or the cross thinner.

Locate the filled close and checkmark icon assets and compare their stroke weights, starting with the comparison images in the issue. Adjust the filled variants so their visual weights are consistent, then verify the close/checkmark pairs in the outline, filled, and sharp styles.

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