docs: correct pubkey param descriptions for secp256k1_keypair_{xonly_,}pub #1341

1. 
   theStack commented at 4:48 pm on June 11, 2023: contributor

   From an API perspective, the functions secp256k1_keypair_pub and secp256k1_keypair_xonly_pub always succeed (i.e. return the value 1), so the other cases in the pubkey parameter descriptions never happen and can hence be removed.

   Note that the “1 always” return value description was previously done in commit https://github.com/bitcoin-core/secp256k1/commit/b8f8b99f0fb3a5cd4c6fb1c9c8dfed881839e19e (PR #1089), which also explains why invalid inputs for the affected functions are in practice only possible in violation of the type system.

2. docs: correct `pubkey` param descriptions for `secp256k1_keypair_{xonly_,}pub`

   From an API perspective, the functions `secp256k1_keypair_pub` and
   `secp256k1_keypair_xonly_pub` always succeed (i.e. return the value 1),
   so the other cases in the `pubkey` parameter descriptions never happen
   and can hence be removed.
   
   Note that the "1 always" return value description was previously done in
   commit b8f8b99f0fb3a5cd4c6fb1c9c8dfed881839e19e (PR #1089), which also
   explains why invalid inputs for the affected functions are in practice
   only possible in violation of the type system.

   f3644287b1
3. real-or-random added the label documentation on Jun 11, 2023
4. real-or-random approved
5. 
   real-or-random commented at 4:57 pm on June 11, 2023: contributor

   ACK https://github.com/bitcoin-core/secp256k1/pull/1341/commits/f3644287b10cd7339fbb0e35e953235351f5efb6 because it’s consistent with the other docs
6. 
   jonasnick commented at 8:38 am on June 12, 2023: contributor

   ACK f3644287b10cd7339fbb0e35e953235351f5efb6
7. jonasnick merged this on Jun 12, 2023
8. jonasnick closed this on Jun 12, 2023

   ---

9. real-or-random cross-referenced this on Jun 15, 2023 from issue ElligatorSwift + integrated x-only DH by sipa
10. sipa referenced this in commit 901336eee7 on Jun 21, 2023
11. vmta referenced this in commit 8f03457eed on Jul 1, 2023
12. hebasto referenced this in commit 270d2b37b8 on Jul 21, 2023
13. jonasnick cross-referenced this on Jul 26, 2023 from issue Upstream PRs 1314, 1317, 1318, 1316, 1327, 1310, 1328, 1333, 1330, 1334, 1337, 1341, 1339, 1350, 1349, 1338, 1129, 1347, 1336, 1295, 1354, 1355, 1356 by jonasnick

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