message: typo in comment for secp256k1_ec_pubkey_tweak_mul ()
  Summary:
  Fixes a typo in secp256k1.h documentation
  This is a backport of linsecp256k1's PR631
  Test Plan:
  make check
  Reviewers: #bitcoin_abc, jasonbcox
diff: @@ -646,7 +646,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul(
  * uniformly random 32-byte arrays, or equal to zero. 1 otherwise.
  * Args: ctx: pointer to a context object initialized for validation
  * (cannot be NULL).
  - * In/Out: pubkey: pointer to a public key obkect.
  + * In/Out: pubkey: pointer to a public key object.
  * In: tweak: pointer to a 32-byte tweak.
  */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul(
  