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>

libraries/matrix/api/build.gradle.kts

@@ -53,7 +53,6 @@ dependencies {
     implementation(libs.serialization.json)
     implementation(projects.libraries.androidutils)
     implementation(projects.libraries.architecture)
-    implementation(projects.libraries.sessionStorage.api)
     implementation(projects.services.analytics.api)
 
     testCommonDependencies(libs)

libraries/matrix/impl/build.gradle.kts

@@ -68,7 +68,6 @@ dependencies {
     implementation(projects.libraries.di)
     implementation(projects.libraries.featureflag.api)
     implementation(projects.libraries.network)
-    implementation(projects.libraries.preferences.api)
     implementation(projects.libraries.sessionStorage.api)
     implementation(projects.libraries.workmanager.api)
     implementation(projects.services.analytics.api)
@@ -77,14 +76,12 @@ dependencies {
     implementation(projects.libraries.core)
     implementation(variantOf(libs.jna) { artifactType("aar") })
     implementation(libs.androidx.datastore.preferences)
-    implementation(libs.serialization.json)
     implementation(libs.kotlinx.collections.immutable)
 
     testCommonDependencies(libs)
     testImplementation(projects.features.enterprise.test)
     testImplementation(projects.libraries.featureflag.test)
     testImplementation(projects.libraries.matrix.test)
-    testImplementation(projects.libraries.preferences.test)
     testImplementation(projects.libraries.previewutils)
     testImplementation(projects.libraries.sessionStorage.test)
     testImplementation(projects.libraries.workmanager.test)