Fix alpha-shadow-input-default token (#2274)

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## Related Issue

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<!-- Fixes #0000 -->

- None
## Summary

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- `alpha-shadow-input-default` 토큰이 참조하고 있는 값을 수정합니다. 

## Details

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- 생략

### Breaking change? (Yes/No)

<!-- If Yes, please describe the impact and migration path for users -->

- No

## References

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aware of -->

- [디자인
스펙(internal)](https://www.figma.com/design/LIxRAsKKyGx3fdgvm2knL9/%F0%9F%93%8C-Foundation?node-id=40221-32519&t=SFSQo9D9XFaNipko-4)

.changeset/chatty-hounds-bow.md

@@ -0,0 +1,5 @@
+---
+'@channel.io/bezier-tokens': patch
+---
+
+Change `innerShadow` value of `alpha-shadow-input-default` token to reference `color.shadow.medium`

packages/bezier-tokens/src/alpha/semantic/shadow.json

@@ -26,7 +26,7 @@
       "default": {
         "value": [
           {
-            "color": "{color.shadow.base-inner}",
+            "color": "{color.shadow.medium}",
             "type": "innerShadow",
             "x": "0px",
             "y": "0px",