refactor(checkbox): update according to design (#30882)

Issue number: resolves #

---------

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## What is the current behavior?
The checkbox component does not currently match our UX designs for the
ionic theme.

## What is the new behavior?
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this PR. -->
- Changed typography to use correct design token.


## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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screenshots of how the component looks before and after the change. -->

core/src/components/checkbox/checkbox.ionic.scss

@@ -113,7 +113,7 @@ input {
 // ----------------------------------------------------------------
 
 .checkbox-bottom {
-  @include globals.typography(globals.$ion-body-sm-medium);
+  @include globals.typography(globals.$ion-body-md-regular);
 }
 
 .checkbox-bottom .error-text {