fix typo, s/changed/unchanged

src/tests.c

@@ -3177,7 +3177,7 @@ void run_eckey_edge_case_test(void) {
     VG_CHECK(&pubkey, sizeof(pubkey));
     CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) > 0);
     pubkey_negone = pubkey;
-    /* Tweak of zero leaves the value changed. */
+    /* Tweak of zero leaves the value unchanged. */
     memset(ctmp2, 0, 32);
     CHECK(secp256k1_ec_privkey_tweak_add(ctx, ctmp, ctmp2) == 1);
     CHECK(memcmp(orderc, ctmp, 31) == 0 && ctmp[31] == 0x40);