Revert "Cache dependencies for CI jobs (model-checking#4181)"

This reverts commit ada8ed3: caching
.rustup means we just keep piling up toolchains. We already have 6 GB as
cache size, and will eventually just hit the 10 GB limit and not be
caching anything anymore.

We could revisit caching to build something more effective, but also
possible effects of caching are somewhat negligible anyway.

Author: tautschnig

.github/workflows/bench-compiler.yml

@@ -39,18 +39,6 @@ jobs:
           ref: ${{ env.NEW_REF }}
           fetch-depth: 1
 
-      - name: Cache Kani build artifacts
-        uses: Swatinem/rust-cache@v2
-        with:
-          cache-on-failure: true
-          shared-key: "kani-rust-cache-bench"
-          workspaces: |
-            new
-            new/tools/compile-timer
-            old
-            old/tools/compile-timer
-          cache-directories: "~/.rustup"
-
       - name: Set up Kani Dependencies (old variant)
         uses: ./old/.github/actions/setup
         with:
@@ -115,18 +103,6 @@ jobs:
           ref: ${{ env.NEW_REF }}
           fetch-depth: 1
 
-      - name: Cache Kani build artifacts
-        uses: Swatinem/rust-cache@v2
-        with:
-          cache-on-failure: true
-          shared-key: "kani-rust-cache-bench"
-          workspaces: |
-            new
-            new/tools/compile-timer
-            old
-            old/tools/compile-timer
-          cache-directories: "~/.rustup"
-
       - name: Set up Kani Dependencies (old variant)
         uses: ./old/.github/actions/setup
         with:

.github/workflows/kani.yml

@@ -23,13 +23,6 @@ jobs:
       - name: Checkout Kani
         uses: actions/checkout@v5
 
-      - name: Cache Kani build artifacts
-        uses: Swatinem/rust-cache@v2
-        with:
-          cache-on-failure: true
-          shared-key: "kani-rust-cache-dev"
-          cache-directories: "~/.rustup"
-
       - name: Setup Kani Dependencies
         uses: ./.github/actions/setup
         with:
@@ -50,13 +43,6 @@ jobs:
           sudo apt-get install -y python3-pip
           pushd tools/benchcomp && pip3 install -r requirements.txt
 
-      - name: Cache Kani build artifacts
-        uses: Swatinem/rust-cache@v2
-        with:
-          cache-on-failure: true
-          shared-key: "kani-rust-cache-release"
-          cache-directories: "~/.rustup"
-
       - name: Setup Kani Dependencies
         uses: ./.github/actions/setup
         with:
@@ -74,13 +60,6 @@ jobs:
       - name: Checkout Kani
         uses: actions/checkout@v5
 
-      - name: Cache Kani build artifacts
-        uses: Swatinem/rust-cache@v2
-        with:
-          cache-on-failure: true
-          shared-key: "kani-rust-cache-release"
-          cache-directories: "~/.rustup"
-
       - name: Setup Kani Dependencies
         uses: ./.github/actions/setup
         with:
@@ -97,12 +76,6 @@ jobs:
       - name: Checkout Kani
         uses: actions/checkout@v5
 
-      - name: Cache Kani build artifacts
-        uses: Swatinem/rust-cache@v2
-        with:
-          cache-on-failure: true
-          cache-directories: "~/.rustup"
-
       - name: Setup Kani Dependencies
         uses: ./.github/actions/setup
         with:

.github/workflows/verify-std-check.yml

@@ -43,14 +43,6 @@ jobs:
           path: kani
           fetch-depth: 0
 
-      - name: Cache Kani build artifacts
-        uses: Swatinem/rust-cache@v2
-        with:
-          cache-on-failure: true
-          workspaces: kani
-          shared-key: "kani-rust-cache-dev"
-          cache-directories: "~/.rustup"
-
       - name: Setup Kani Dependencies
         uses: ./kani/.github/actions/setup
         with: