Remove not-needed #include

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index 4e28f30..2b4afd7 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -21,8 +21,6 @@
 #ifndef PSA_CRYPTO_CORE_H
 #define PSA_CRYPTO_CORE_H
 
-#include "mbedtls/constant_time.h"
-
 #include "mbedtls/build_info.h"
 
 #include "psa/crypto.h"