github: increase parallelism in windows build

.github/workflows/main.yml

@@ -259,7 +259,7 @@ jobs:
           go-version: '${{ env.GO_VERSION }}'
 
       - name: run itest
-        run: make itest-parallel windows=1 tranches=2 parallel=2 timeout=180m
+        run: make itest-parallel windows=1
 
       - name: Zip log files on failure
         if: ${{ failure() }}