Bump signature from 1.6.0 to 2.0.0

Bumps signature from 1.6.0 to 2.0.0.

Commits

115d231 signature v2.0.0 (#1211)
fa1fec4 signature: rename *-preview features to crate names (#1210)
d041d1f signature: use doc_auto_cfg (#1209)
ca920c6 elliptic-curve: add BlindedScalar (#1208)
c394a02 elliptic-curve: add NonZeroScalar::invert_vartime (#1207)
322377a elliptic-curve: use CryptoRngCore trait (#1206)
e835a1c elliptic-curve: improve SecretKey impl for Debug (#1205)
a238514 elliptic-curve: mandate scalar::FromUintUnchecked (#1204)
6c519b0 elliptic-curve: rename ScalarCore to ScalarPrimitive (#1203)
adb5baa elliptic-curve: rename SecretKey::to_sec1_pem (#1202)
Additional commits viewable 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)

Revertron / Alfis

Bump signature from 1.6.0 to 2.0.0 #334