removing a leftover printf from debug

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index 6e6a6c2..3cea351 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -950,7 +950,6 @@
     ((void) md_alg);
 
     if (curve == 0) {
-        fprintf(stderr, "unkown curve!\n");
         return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
     }