[github actions] changed root-reserve size (#1786)

## Summary
Github action ubuntu image has been reduced. This fixes the error with
Maximize build disk space step.

## How was it tested?
github actions

Author: mohsenari

.github/workflows/cli-tests.yaml

@@ -147,7 +147,7 @@ jobs:
         uses: easimon/maximize-build-space@v8
         if: matrix.os == 'ubuntu-latest'
         with:
-          root-reserve-mb: 40000
+          root-reserve-mb: 32768
           temp-reserve-mb: 10000
           remove-dotnet: true
           remove-android: true