fix(build): drop vergen-git2 build dependency

vergen-git2 reads git metadata at build time, but the crates.io source
tarball ships no .git, so the published 1.1.0 fails on `cargo install`.
crates.io versions are immutable (no overwrite) and Chocolatey's
moderation queue blocks a fast re-push, so a clean 1.1.1 without vergen
is the only fix.

Cargo.toml

@@ -118,7 +118,6 @@ serial_test = "3"
 
 [build-dependencies]
 cfg_aliases = "0.2"
-vergen-git2 = { version = "10", features = ["build", "cargo", "rustc", "si"] }
 
 [[bin]]
 name = "termscp"