[rust] update dependencies' version constraints

rust/Cargo.toml

@@ -23,19 +23,19 @@ categories = [
 keywords = ["tui", "cli", "terminal", "ncurses", "ffi"]
 
 [dependencies]
-libc = {version = ">= 0.2.80", default-features = false}
-cty = ">= 0.2.1"
+libc = { version = "^0.2.80", default-features = false }
+cty = "^0.2.1"
 
 [build-dependencies]
-bindgen = ">= 0.55.1"
-pkg-config = ">= 0.3.18"
+bindgen = "^0.55.1"
+pkg-config = "^0.3.18"
 
 [dev-dependencies]
-serial_test = ">= 0.5.0"
-serial_test_derive = ">= 0.5.0"
+serial_test = "^0.5.0"
+serial_test_derive = "^0.5.0"
 
 # for the examples
-rand = ">= 0.8"
+rand = "^0.8"
 
 # https://doc.rust-lang.org/cargo/reference/profiles.html
 [profile.dev]