build: bump MSRV to 1.81 (#264)

Some underlying dependencies (e.g `home`) updated their MSRV within a
compatible version update.

`home` is used by several important deps (e.g `bollard`), so it's
already affected users of the crate

However, it's common practice to use newer rust version for testing (in
CI and etc)

Cargo.toml

@@ -4,7 +4,7 @@ version = "0.11.4"
 description = "Community maintained modules for Testcontainers for Rust"
 categories = ["development-tools::testing"]
 edition = "2021"
-rust-version = "1.75"
+rust-version = "1.81"
 repository = "https://github.com/testcontainers/testcontainers-rs-modules-community"
 keywords = ["docker", "testcontainers"]
 license = "MIT"