Do not report detekt LargeClass issues on test classes (#7713)

detekt's default configuration excludes test source sets from
`TooManyFunctions` and `StringLiteralDuplication`, but not from
`LargeClass`, so large test classes were reported and had to carry a
`@Suppress("LargeClass")` annotation.

Add the same kind of exclusion to the `LargeClass` rule in
`tools/detekt/detekt.yml` and remove the 24 now-redundant suppressions
from test files. The two remaining suppressions are in production code,
where the rule still applies.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

features/preferences/impl/src/test/kotlin/io/element/android/features/preferences/impl/notifications/NotificationSettingsPresenterTest.kt

@@ -45,7 +45,6 @@ import kotlinx.coroutines.test.runTest
 import org.junit.Test
 import kotlin.time.Duration.Companion.milliseconds
 
-@Suppress("LargeClass")
 class NotificationSettingsPresenterTest {
     @Test
     fun `present - ensures initial state is correct`() = runTest {