[crypto] remove unused references to get key attributes (#7009)

Removing some unused references to get key attribute feature.

include/openthread/instance.h

@@ -53,7 +53,7 @@ extern "C" {
  * @note This number versions both OpenThread platform and user APIs.
  *
  */
-#define OPENTHREAD_API_VERSION (162)
+#define OPENTHREAD_API_VERSION (163)
 
 /**
  * @addtogroup api-instance

include/openthread/platform/crypto.h

@@ -40,10 +40,6 @@
 
 #include <openthread/error.h>
 
-#ifdef OT_PLAT_CRYPTO_ATTRIBUTES_TYPE_HEADER
-#include OT_PLAT_CRYPTO_ATTRIBUTES_TYPE_HEADER
-#endif
-
 #ifdef __cplusplus
 extern "C" {
 #endif

src/core/crypto/storage.hpp

@@ -96,12 +96,6 @@ typedef otCryptoKeyRef KeyRef;
 
 constexpr KeyRef kInvalidKeyRef = 0x80000000; ///< Invalid `KeyRef` value (PSA_KEY_ID_VENDOR_MAX + 1).
 
-/**
- * This type represents the Key Attributes structure.
- *
- */
-typedef otCryptoKeyAttributes KeyAttributes;
-
 /**
  * Determine if a given `KeyRef` is valid or not.
  *