chore: Bump MSRV to 1.85

Author: epage

Cargo.toml

@@ -5,7 +5,7 @@ resolver = "2"
 repository = "https://github.com/rust-cli/rexpect"
 license = "MIT OR Apache-2.0"
 edition = "2021"
-rust-version = "1.70.0"  # MSRV
+rust-version = "1.85.0"  # MSRV
 include = [
   "build.rs",
   "src/**/*",