fix the installation of Rust in the CI

!39 (merged) and !40 (merged) changed the CI to use a toolchain file.

however, having default as the $.profile causes extra useless components to be installed.

this MR sets the $.profile to minimal in the toolchain file and the $.components to rustfmt and clippy.

.gitlab-ci.yml

@@ -19,8 +19,6 @@ workflow:
 
 fmt:
   stage: fmt
-  before_script:
-    - rustup component add rustfmt
 
   script:
     - cargo fmt --all -- --check
@@ -34,8 +32,6 @@ test:
     - apt upgrade --yes
     - apt install protobuf-compiler --yes
 
-    - rustup component add clippy
-
     - rustup --version
     - rustup show --verbose
     - rustc --version