Update secp256k1 requirement from 0.21 to 0.22

[dependabot[bot]]

Updates the requirements on secp256k1 to permit the latest version.

Changelog

Sourced from secp256k1's changelog.

0.22.0 - 2022-03-08

• Disable bitcoin_hashes/std by default; add bitcoin-hashes-std feature to re-enable it
• Rename more schnorrsig methods to schnorr
• Obfuscate SharedSecret string serialization
• Simplify SharedSecret API to use a 32-byte buffer; users of custom hashes should now use bare arrays rather than this type.
• Change serde serialization of Parity from i32 to u8; clean up error handling

0.21.3 - 2022-01-31

• Several documentation improvements (#366, #365, #373, #381, #369, #389, #391, #397, #399, #340)
• Deprecate the generate_schnorrsig_keypair method (unclear value)
• Add serde traits to KeyPair
• Redo the API of the new Parity type to more clearly match our desired semantics; the From<i32> impl on this type is now deprecated. Also #400.
• Randomize the global context on creation when possible; weaken global-context-less-secure feature accordingly.
• Improve the global context API
• Fix the Debug impl for RecoverableSignature
• Implement LowerHex and Display

0.21.0 - 2022-01-02

• Fix KeyPair::from_seckey_slice error return value
• Reduce the lowmemory precomp table size
• Add KeyPair::serialize_sec
• Increase bitcoin_hashes version to 0.10; rename secp256k1::bitcoin_hashes module to secp256k1::hashes to align with bitcoin crate naming
• Add new error variant for PublicKey::combine_keys
• Change Display and Debug for secret keys to only output a truncated hash
• Improve documentation
• Implement Hash for schnorrsig::Signature
• Refactor modules to put Schnorr and ECDSA on more equal footing
• Add serde traits for KeyPair type
• Fix context bound requirements for a few methods
• Add a static immutable-zero aligned type
• Change tweak_add_assign and tweak_add_check to use an opaque Parity type rather than a boolean

0.20.3 - 2021-06-10

• Fix SecretKey validation in from_str
• Add global-context-less-secure feature which creates a non-randomized global context (and does not require rand or std)
• Add schnorrsig::KeyPair::from_secret_key convenience function
• Add combine_keys function to PublicKey
• Reduce symbol visibility in C compilation to allow LTO to work
• Add alloc feature requiring rustc 1.36+ to enable context creation without std
• Rewrite stubbed-out-for-fuzzing version of the library to improve fuzzer accessibility

0.20.2 - 2021-04-27

• Fix some WASM build issues
• Add some missing #derives to Error
• Add serde support for Schnorr signatures and for deserializing from owned types

... (truncated)

Commits

• See full diff in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR: - `@dependabot rebase` will rebase this PR - `@dependabot recreate` will recreate this PR, overwriting any edits that have been made to it - `@dependabot merge` will merge this PR after your CI passes on it - `@dependabot squash and merge` will squash and merge this PR after your CI passes on it - `@dependabot cancel merge` will cancel a previously requested merge and block automerging - `@dependabot reopen` will reopen this PR if it is closed - `@dependabot close` will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually - `@dependabot ignore this major version` will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this minor version` will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself) - `@dependabot ignore this dependency` will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)

[dependabot[bot]]

Superseded by #649.