test(android): pin SvgIconCacheTest to Robolectric SDK 28

[dcalhoun]

What?

Fix unexpected SvgIconCacheTest failure due to missing config introduced in #642.

Why?

Prevent blocking CI failures.

How?

Add the @Config(sdk = [28]) found in other Android tests to align with the current practice.

Testing Instructions

N/A, no user-facing changes.

Accessibility Testing Instructions

N/A, no user-facing changes.

Screenshots or screencast

N/A, no user-facing changes.

---

AI-generated details

Problem: Trunk's :android: Test Android Library job fails (build 2997): SvgIconCacheTest > classMethod FAILED — UnsupportedOperationException at DefaultSdkProvider.java:174.

Cause: #642 enabled isIncludeAndroidResources, so Robolectric now defaults to the project's SDK 36, which requires Java 21. CI runs an older JVM. SvgIconCacheTest was the only Robolectric class without an explicit @Config(sdk = [28]). Local runs pass on Java 21, which hid it.

Fix: Pin the class to SDK 28 like the others.

Testing: CI's :android: Test Android Library passes. Locally: android/gradlew -p android :Gutenberg:testDebugUnitTest --tests "org.wordpress.gutenberg.inserter.SvgIconCacheTest".

🤖 Generated with Claude Code

[wpmobilebot]

XCFramework Build

This PR's XCFramework is available for testing. Add the following to your Package.swift:

.package(url: "https://github.com/wordpress-mobile/GutenbergKit", branch: "pr-build/723")

_{Built from 87b2075}

[nbradbury]

@dcalhoun Claude had a few findings, but they don't appear to be important. I'll approve and leave it to you to determine if anything needs changing.

Severity	Location	Issue	Impact
Low	SvgIconCacheTest.kt:18	The fix adds a fourth per-class @Config(sdk = [28]) rather than pinning the SDK once with sdk=28 in src/test/resources/robolectric.properties, a file that doesn't exist yet.	If the next Robolectric test class is added without the annotation, it defaults to SDK 36, which needs Java 21, so it passes locally and fails on CI with the same UnsupportedOperationException from DefaultSdkProvider.
Low	build.gradle.kts:92	The actual cause is that CI runs tests on an older JVM than the one needed for the SDK 36 that Robolectric now resolves, and the PR works around this in each test class instead of fixing it in the build.	Local runs on Java 21 and CI runs keep resolving Robolectric SDKs differently, so any test without a pin can stay green locally and only fail on CI.
Low	SvgIconCacheTest.kt:18	With SDK 28 pinned, the test never checks the Color.parseColor/Color.argb behaviour it relies on against SDK 36, which the library compiles against.	A named-colour parsing regression that only shows up on newer APIs would pass this suite without being caught.

[nbradbury]

LGTM

[dcalhoun]

Thanks! I'll merge to unblock CI and other PRs. We can follow up on the findings separately if deemed worthwhile.