If you marked that you dont want it, you dont get it.
But i found an Fix,
1. mark that you dont want it.
2. Go into the installation folder, there should be 1 file and 2 folders, rename the file Construct2.exe to Construct231.exe
3. Now mark that you want the beta update. (In Steam)
4. Let steam update it.
5. When the download is finished, rename the Construct231.exe to Construct2.exe
6. Launch the new r140 beta through Steam!