Merge bitcoin#857: docs: fix simple typo, dependecy -> dependency

18aadf9 docs: fix simple typo, dependecy -> dependency (Tim Gates)

Pull request description:

  There is a small typo in src/group_impl.h.

  Should read `dependency` rather than `dependecy`.

ACKs for top commit:
  real-or-random:
    ACK 18aadf9

Tree-SHA512: 3529f43bcc87ea8940ecf5af765951f61d97d1efa86fd8abc29e32b600fd449165a94a2fa525bc6b3d9a7d8aa6e691cc4d42033537b196ba166a867e6db7f397

src/group_impl.h

@@ -674,7 +674,7 @@ static int secp256k1_ge_is_in_correct_subgroup(const secp256k1_ge* ge) {
     secp256k1_gej out;
     int i;
 
-    /* A very simple EC multiplication ladder that avoids a dependecy on ecmult. */
+    /* A very simple EC multiplication ladder that avoids a dependency on ecmult. */
     secp256k1_gej_set_infinity(&out);
     for (i = 0; i < 32; ++i) {
         secp256k1_gej_double_var(&out, &out, NULL);