psa: Make psa_set_key_lifetime() match declaration

Previously, the psa_set_key_lifetime() implementation did not match the
function declaration in psa/crypto.h. Value types don't need const,
since they are passed by value. Fix psa_set_key_lifetime()
implementation by making it match its declaration in the header.
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 8ce668c..7d78827 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -2513,7 +2513,7 @@
 }
 
 psa_status_t psa_set_key_lifetime( psa_key_slot_t key,
-                                   const psa_key_lifetime_t lifetime )
+                                   psa_key_lifetime_t lifetime )
 {
     key_slot_t *slot;