Remove usless pre-cache task

We are not cleaning the rest of xtask artifacts, so this effectively
does nothing. xtask is small and changes rarely, so this shouldn't
really matter.

.github/workflows/ci.yaml

@@ -70,10 +70,6 @@ jobs:
     - name: Prepare cache
       run: cargo xtask pre-cache
 
-    - name: Prepare cache 2
-      if: matrix.os == 'windows-latest'
-      run: Remove-Item ./target/debug/xtask.exe, ./target/debug/deps/xtask.exe
-
   # Weird targets to catch non-portable code
   rust-cross:
     name: Rust Cross