fix(deps): update dependency dev.zacsweers.kctfork:core to v0.12.0 (#2173)

This PR contains the following updates:

| Package | Change |
[Age](https://docs.renovatebot.com/merge-confidence/) |
[Confidence](https://docs.renovatebot.com/merge-confidence/) |
|---|---|---|---|
|
[dev.zacsweers.kctfork:core](https://redirect.github.com/zacsweers/kotlin-compile-testing)
| `0.11.1` -> `0.12.0` |
![age](https://developer.mend.io/api/mc/badges/age/maven/dev.zacsweers.kctfork:core/0.12.0?slim=true)
|
![confidence](https://developer.mend.io/api/mc/badges/confidence/maven/dev.zacsweers.kctfork:core/0.11.1/0.12.0?slim=true)
|

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---

### Release Notes

<details>
<summary>zacsweers/kotlin-compile-testing
(dev.zacsweers.kctfork:core)</summary>

###
[`v0.12.0`](https://redirect.github.com/zacsweers/kotlin-compile-testing/blob/HEAD/CHANGELOG.md#0120)

[Compare
Source](https://redirect.github.com/zacsweers/kotlin-compile-testing/compare/0.11.1...0.12.0)

*2025-12-16*

- Update to Kotlin `2.3.0`.
- Remove `KEEP_KDOC_COMMENTS_IN_STUBS` kapt option as it was removed
upstream.
- Remove `supportsK2` entirely, only K2 is supported going forward.

</details>

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github-workflows-kt/build.gradle.kts

@@ -30,7 +30,7 @@ dependencies {
     implementation(projects.sharedInternal)
     ksp(projects.codeGenerator)
 
-    testImplementation("dev.zacsweers.kctfork:core:0.11.1")
+    testImplementation("dev.zacsweers.kctfork:core:0.12.0")
     // Needed to use the right version of the compiler for the libraries that depend on it.
     testImplementation(kotlin("compiler"))
     testImplementation(kotlin("reflect"))