Bump crossbeam-channel from 0.5.4 to 0.5.6

[dependabot[bot]]

Bumps crossbeam-channel from 0.5.4 to 0.5.6.

Release notes

Sourced from crossbeam-channel's releases.

crossbeam-channel 0.5.6

• Bump the minimum supported Rust version to 1.38. (#877)

crossbeam-channel 0.5.5

• Replace Spinlock with Mutex. (#835)

Commits

• 5e0f59a Merge #880
• 0f4092b Prepare for the next release
• 6dc9be5 Merge #879
• f2ca66b epoch: Adjust MAX_OBJECTS
• c059aec Merge #877
• 6ac1232 Favor .cast() over as
• b553b4f Use const_in_array_repeat_expressions
• 0e14971 Bump MSRV to Rust 1.38
• 99b14b1 Merge #875 #876
• 371de8c Miri: Fix thread leaks in doctests in utils
• Additional commits viewable in compare view

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