ci: Bump actions/{checkout,cache} to v3

This gets rid of the deprecation warnings about
https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

.github/workflows/nix.yml

@@ -20,7 +20,7 @@ jobs:
             experimental-features = nix-command flakes
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
       - name: Clone project
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Build
         # "nix build" builds with full optimization and includes a profiling
         # build, so just the build of xmonad-contrib itself takes 3 minutes.

.github/workflows/packdeps.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Clone project
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Setup Haskell
         uses: haskell/actions/setup@v1
         with:

.github/workflows/stack.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
       - name: Clone project
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Prepare apt sources
         run: |
@@ -59,13 +59,13 @@ jobs:
           date +date=1-%Y-%m >> $GITHUB_OUTPUT
 
       - name: Cache Haskell package metadata
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: ~/.stack/pantry
           key: stack-pantry-${{ runner.os }}-${{ steps.cache-date.outputs.date }}
 
       - name: Cache Haskell dependencies
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: |
             ~/.stack/*