test runner: remove placeholder version from Cargo.toml

`version` is optional in Rust/Cargo 1.75 and later.  The test runner already requires Rust >= 1.80, and the value that was set for `version` matches what would be used in the absence of `version`.

tests/Cargo.toml

@@ -1,6 +1,5 @@
 [package]
 name    = "tests"
-version = "0.0.0"
 authors = ["Casey Rodarmor <[email protected]>", "Noah Bogart <[email protected]"]
 edition = "2021"
 default-run = "tests"