ci(lesavka): use image rustup toolchain

Jenkinsfile

@@ -23,8 +23,6 @@ spec:
       env:
         - name: CARGO_HOME
           value: /home/jenkins/agent/.cargo-home
-        - name: RUSTUP_HOME
-          value: /home/jenkins/agent/.rustup-home
         - name: CARGO_TARGET_DIR
           value: /home/jenkins/agent/workspace/lesavka/target
       resources:
@@ -62,7 +60,6 @@ spec:
     CARGO_TERM_COLOR = 'always'
     CARGO_BUILD_JOBS = '1'
     CARGO_HOME = "${WORKSPACE}/.cargo-home"
-    RUSTUP_HOME = "${WORKSPACE}/.rustup-home"
     CARGO_TARGET_DIR = "${WORKSPACE}/target"
     PATH = "${WORKSPACE}/.cargo-home/bin:/usr/local/cargo/bin:${PATH}"
     DOCKER_BUILDKIT = '1'