build(deps): bump once_cell from 1.5.2 to 1.6.0

Bumps [once_cell](https://github.com/matklad/once_cell) from 1.5.2 to 1.6.0.
- [Release notes](https://github.com/matklad/once_cell/releases)
- [Changelog](https://github.com/matklad/once_cell/blob/master/CHANGELOG.md)
- [Commits](https://github.com/matklad/once_cell/compare/v1.5.2...v1.6.0)

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.lock

@@ -2025,9 +2025,9 @@ checksum = "8d3b63360ec3cb337817c2dbd47ab4a0f170d285d8e5a2064600f3def1402397"
 
 [[package]]
 name = "once_cell"
-version = "1.5.2"
+version = "1.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "13bd41f508810a131401606d54ac32a467c97172d74ba7662562ebba5ad07fa0"
+checksum = "4ad167a2f54e832b82dbe003a046280dceffe5227b5f79e08e363a29638cfddd"
 
 [[package]]
 name = "opaque-debug"

zebra-consensus/Cargo.toml

@@ -9,7 +9,7 @@ edition = "2018"
 chrono = "0.4.19"
 displaydoc = "0.1.7"
 jubjub = "0.6.0"
-once_cell = "1.5"
+once_cell = "1.6"
 rand = "0.7"
 redjubjub = "0.2"
 serde = { version = "1", features = ["serde_derive"] }

zebra-state/Cargo.toml

@@ -34,7 +34,7 @@ zebra-chain = { path = "../zebra-chain", features = ["proptest-impl"] }
 zebra-test = { path = "../zebra-test/" }
 
 color-eyre = "0.5.10"
-once_cell = "1.5"
+once_cell = "1.6"
 spandoc = "0.2"
 tempdir = "0.3.7"
 tokio = { version = "0.3.6", features = ["full"] }

zebrad/Cargo.toml

@@ -51,7 +51,7 @@ vergen = "3.2.0"
 
 [dev-dependencies]
 abscissa_core = { version = "0.5", features = ["testing"] }
-once_cell = "1.5"
+once_cell = "1.6"
 tempdir = "0.3.7"
 zebra-test = { path = "../zebra-test" }