use ubuntu image in screenshot workflow

.github/workflows/take_screenshot.yml

@@ -16,7 +16,7 @@ env:
 
 jobs:
   build:
-    runs-on: macos-latest
+    runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
 
@@ -29,15 +29,10 @@ jobs:
     - name: Build
       run: cargo build --release --features selfie
 
-    - name: Hide Dock
-      run: defaults write com.apple.dock autohide -bool true && killall Dock
-
     - name: Run and take screenshot
       run: |
         cargo run --release --features selfie > cargo.log 2>&1 &
         sleep 5
-        screencapture fullscreen.png
-
 
     - name: Commit and push screenshot
       run: |
@@ -53,4 +48,3 @@ jobs:
         name: screenshot
         path: |
           screenshot.png
-          fullscreen.png