Remove unused build dependency

It's been like that for a while!

Cargo.lock

@@ -385,7 +385,6 @@ dependencies = [
  "rayon",
  "rgb",
  "rustc-hash",
- "rustc_version",
  "zopfli",
 ]
 
@@ -458,15 +457,6 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "08d43f7aa6b08d49f382cde6a7982047c3426db949b1424bc4b7ec9ae12c6ce2"
 
-[[package]]
-name = "rustc_version"
-version = "0.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bfa0f585226d2e68097d4f95d113b15b83a82e819ab25717ec0590d9584ef366"
-dependencies = [
- "semver",
-]
-
 [[package]]
 name = "rustix"
 version = "0.38.32"
@@ -480,12 +470,6 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
-[[package]]
-name = "semver"
-version = "1.0.22"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "92d43fe69e652f3df9bdc2b85b2854a0825b86e4fb76bc44d945137d053639ca"
-
 [[package]]
 name = "simd-adler32"
 version = "0.3.7"

Cargo.toml

@@ -80,7 +80,6 @@ version = "0.25.1"
 [build-dependencies]
 clap = "4.5.4"
 clap_mangen = "0.2.20"
-rustc_version = "0.4.0"
 
 [features]
 binary = ["dep:clap", "dep:glob", "dep:env_logger"]