Return Unit from ReactiveVaultOperations.awaitDelete(…).

See gh-472.

spring-vault-core/src/main/kotlin/org/springframework/vault/core/ReactiveVaultOperationsExtensions.kt

@@ -86,5 +86,6 @@ suspend fun ReactiveVaultOperations.awaitWrite(path: String, body: Any): VaultRe
  * @author Mark Paluch
  * @since 2.2
  */
-suspend fun ReactiveVaultOperations.awaitDelete(path: String) = delete(path).awaitFirstOrNull()
-
+suspend fun ReactiveVaultOperations.awaitDelete(path: String) {
+    delete(path).awaitFirstOrNull()
+}

spring-vault-core/src/test/kotlin/org/springframework/vault/core/ReactiveVaultOperationsExtensionsTests.kt

@@ -132,7 +132,7 @@ class ReactiveVaultOperationsExtensionsTests {
         every { operation.delete("path") } returns Mono.empty()
 
         runBlocking {
-            assertThat(operation.awaitDelete("path")).isNull()
+            assertThat(operation.awaitDelete("path")).isEqualTo(Unit)
         }
 
         verify {