md_alg is used in ecdsa_sign_wrap(), cleanup code

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index 4df2a2f..663b72d 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -870,7 +870,6 @@
     size_t curve_bits;
     psa_ecc_family_t curve =
         mbedtls_ecc_group_to_psa( ctx->grp.id, &curve_bits );
-    ((void) md_alg);
 
     /* PSA has its own RNG */
     ((void) f_rng);