chore(deps): update dependency org.jetbrains.kotlin.multiplatform to v1.8.21 (#70)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [org.jetbrains.kotlin.multiplatform](https://kotlinlang.org/)
([source](https://togithub.com/JetBrains/kotlin)) | `1.8.20` -> `1.8.21`
|
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|
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|
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|
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|

---

### Release Notes

<details>
<summary>JetBrains/kotlin</summary>

###
[`v1.8.21`](https://togithub.com/JetBrains/kotlin/blob/HEAD/ChangeLog.md#&#8203;1821)

##### Compiler

- [`KT-57848`](https://youtrack.jetbrains.com/issue/KT-57848) Native:
compilation of dynamic/static library fails with Xcode 14.3
- [`KT-57875`](https://youtrack.jetbrains.com/issue/KT-57875) Native
compilation failure: Suspend functions should be lowered out at this
point, but FUN LOCAL_FUNCTION_FOR_LAMBDA
- [`KT-57946`](https://youtrack.jetbrains.com/issue/KT-57946) KAPT:
"RuntimeException: No type for expression" with delegate

##### JavaScript

- [`KT-57356`](https://youtrack.jetbrains.com/issue/KT-57356) KJS:
StackOverflowException on
[@&#8203;JsExport](https://togithub.com/JsExport) with type parameters
referring to one another

##### Tools. Compiler plugins. Serialization

- [`KT-58067`](https://youtrack.jetbrains.com/issue/KT-58067)
Serialization: NullPointerException caused by
[@&#8203;Contextual](https://togithub.com/Contextual) property with type
with generic
- [`KT-57730`](https://youtrack.jetbrains.com/issue/KT-57730)
Serialization: "IllegalStateException: Serializer for element of type
<root>.Foo has not been found" caused by serialization of Java type

##### Tools. Gradle. JS

- [`KT-57766`](https://youtrack.jetbrains.com/issue/KT-57766) KJS /
Gradle "Module not found: Error: Can't resolve
'kotlin-kotlin-stdlib-js-ir'" when using "useEsModules"

##### Tools. Kapt

- [`KT-58027`](https://youtrack.jetbrains.com/issue/KT-58027) Kotlin
1.8.20 kapt issue "null: KtCallExpression: build()"

##### Tools. Maven

- [`KT-58048`](https://youtrack.jetbrains.com/issue/KT-58048) Maven:
"Too many source module declarations found" after upgrading to 1.8.20
- [`KT-58101`](https://youtrack.jetbrains.com/issue/KT-58101) 'Unable to
access class' in kotlin-maven-plugin after updating to Kotlin 1.8.20

</details>

---

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Author: renovate[bot]

gradle/libs.versions.toml

@@ -1,5 +1,5 @@
 [versions]
-kotlin = "1.8.20"
+kotlin = "1.8.21"
 junit = "5.9.3"
 detekt = "1.22.0"