library: Remove unused psa_crypto_core.h include

Remove unused psa_crypto_core.h include.
The PSA util file provides helper functions when using the PSA API.
It should not rely on PSA internal headers, and instead only use
public headers.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>
diff --git a/library/psa_util.c b/library/psa_util.c
index 0225bbf..b462d18 100644
--- a/library/psa_util.c
+++ b/library/psa_util.c
@@ -12,7 +12,6 @@
 
 #include <psa/crypto.h>
 
-#include "psa_crypto_core.h"
 #include "psa_util_internal.h"
 
 /* The following includes are needed for MBEDTLS_ERR_XXX macros */