chore(deps): Update Rust crate downcast-rs to v2

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
downcast-rs	dependencies	major	1.2.1 -> 2.0.0

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Release Notes

marcianx/downcast-rs (downcast-rs)

v2.0.1

Compare Source

Change

• Updated how code conditioned on the sync flag is written in the crate
  documentation to work around a crates.io doc rendering
  bug.

v2.0.0

Compare Source

Added

• Gated the sync/Arc downcasting functionality behind a new sync feature
  that is enabled by default.
• Added a new DowncastSend trait to support downcasting to Box<Any + Send>
  and made DowncastSync extend this trait.
• Added downcasting support to Box<Any + Send + Sync> to DowncastSync.

Change

• Updated minimum supported rust version 1.56 to enforce the
  rustdoc::bare_urls lint (1.53) and switch to edition 2021 (1.56).

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[coveralls]

Pull Request Test Coverage Report for Build 13599901262

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.04%) to 29.191%

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Files with Coverage Reduction	New Missed Lines	%
src/legacy/git/repo.rs	1	45.83%

Totals
Change from base Build 13573705971:	0.04%
Covered Lines:	1628
Relevant Lines:	5577

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💛 - Coveralls