Remove unused Gradle dependencies

Remove dependencies flagged as unused by the Dependency Analysis Gradle Plugin
(`./gradlew buildHealth`) and explicitly declared in module build files.

Removals were skipped when the dependency provides transitively something the
module (or a consumer of an `api` dependency) uses directly, as well as for
runtime-only dependencies (element-call-embedded, sentry-android,
rustls-platform-verifier). Dependencies added by the convention plugin helpers
(composeDependencies, testCommonDependencies) are left untouched.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

features/callnative/impl/build.gradle.kts

@@ -47,8 +47,6 @@ dependencies {
     testCommonDependencies(libs)
     testImplementation(libs.element.call.test)
     testImplementation(projects.features.call.test)
-    testImplementation(projects.libraries.featureflag.test)
     testImplementation(projects.libraries.matrix.test)
-    testImplementation(projects.libraries.preferences.test)
     testImplementation(projects.services.appnavstate.test)
 }