CI/check: use a fresh msys2

Like in the other steps.
The staging update makes it slower since that also updates other packages
provided by the host, and it updates packages installed by the action itself,
in case they are in staging.

.github/workflows/main.yml

@@ -137,8 +137,9 @@ jobs:
         if: steps.check-run.outputs.run == 'true'
         with:
           msystem: UCRT64
+          update: true
+          release: ${{ runner.arch != 'ARM64' }}
           install: mingw-w64-ucrt-x86_64-python-pip mingw-w64-ucrt-x86_64-python-pacdb
-          release: false # since we aren't building anything
       - name: Add staging repo
         if: steps.check-run.outputs.run == 'true'
         shell: msys2 {0}