Apply code review changes

Author: EnricoMi

cpp/src/arrow/dataset/file_parquet_encryption_test.cc

@@ -83,8 +83,8 @@ const auto kAllParamValues = ::testing::Values(
     EncryptionTestParam{false, true, true}, EncryptionTestParam{true, true, true});
 
 // Base class to test writing and reading encrypted dataset.
-template <typename T, typename = typename std::enable_if<
-                          std::is_base_of<EncryptionTestParam, T>::value>::type>
+template <typename T, typename = typename std::enable_if_t<
+                          std::is_base_of_v<EncryptionTestParam, T>>>
 class DatasetEncryptionTestBase : public testing::TestWithParam<T> {
  public:
 #ifdef ARROW_VALGRIND

python/pyarrow/tests/test_dataset_encryption.py

@@ -91,7 +91,7 @@ def create_decryption_config():
 def create_kms_connection_config(keys):
     return pe.KmsConnectionConfig(
         custom_kms_conf={
-            key_name: key.decode("UTF-8") if isinstance(key, bytes) else key
+            key_name: key.decode("UTF-8")
             for key_name, key in keys.items()
         }
     )