Remove version-sync dependency and tests

`version-sync` depends on `url`. A patch version of `url` moved from
`unicode-bidi` as a dep to the icu4x ecosystem which has a huge dep tree
and an aggressive MSRV policy. To avoid maintenance churn, remove this
dep and the associated tests.

Author: lopopolo

Cargo.toml

@@ -24,15 +24,6 @@ default = ["std"]
 std = ["alloc"]
 alloc = []
 
-[dev-dependencies]
-
-# Check that crate versions are properly updated in documentation and code when
-# bumping the version.
-[dev-dependencies.version-sync]
-version = "0.9.3"
-default-features = false
-features = ["markdown_deps_updated", "html_root_url_updated"]
-
 [package.metadata.docs.rs]
 # This sets the default target to `x86_64-unknown-linux-gnu` and only builds
 # that target. `strftime-ruby` has the same API and code on all targets.