feat: Update Kotlin 2.0.21-RC release details and small doc change (#4479)

Author: AlejandraPedroza

docs/topics/eap.md

@@ -58,13 +58,13 @@ check [our instructions on how to configure your build to support this version](
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-        <td><strong>2.0.21-RC</strong>
-            <p>Released: <strong>October 1, 2024</strong></p>
-            <p><a href="https://github.com/JetBrains/kotlin/releases/tag/v2.0.21-RC" target="_blank">Release on GitHub</a></p>
+        <td><strong>2.0.21</strong>
+            <p>Released: <strong>October 10, 2024</strong></p>
+            <p><a href="https://github.com/JetBrains/kotlin/releases/tag/v2.0.21" target="_blank">Release on GitHub</a></p>
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             <p>A bug fix release for Kotlin 2.0.20</p>
-            <p>For more details, please refer to the <a href="https://github.com/JetBrains/kotlin/releases/tag/v2.0.21-RC">changelog</a>.</p>
+            <p>For more details, please refer to the <a href="https://github.com/JetBrains/kotlin/releases/tag/v2.0.21 ">changelog</a>.</p>
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docs/topics/multiplatform/multiplatform-compatibility-guide.md

@@ -15,11 +15,12 @@ with available Gradle, Xcode, and Android Gradle plugin versions:
 
 | Kotlin Multiplatform plugin version | Gradle    | Android Gradle plugin | Xcode |
 |-------------------------------------|-----------|-----------------------|-------|
+| 2.0.21                              | 7.5-8.8*  | 7.4.2–8.5             | 16.0  |
 | 2.0.20                              | 7.5-8.8*  | 7.4.2–8.5             | 15.3  |
 | 2.0.0                               | 7.5-8.5   | 7.4.2–8.3             | 15.3  |
 | 1.9.20                              | 7.5-8.1.1 | 7.4.2–8.2             | 15.0  |
 
-> Kotlin 2.0.20 is fully compatible with Gradle 6.8.3 through 8.6.
+> Kotlin 2.0.20 and 2.0.21 are fully compatible with Gradle 6.8.3 through 8.6.
 > Gradle 8.7 and 8.8 are also supported, but you may see deprecation warnings in your multiplatform projects
 > calling the [`withJava()` function in the JVM target](multiplatform-dsl-reference.md#jvm-targets). 
 > For more information, see the issue in [YouTrack](https://youtrack.jetbrains.com/issue/KT-66542/Gradle-JVM-target-with-withJava-produces-a-deprecation-warning).