revert default value for workbench.tree.expandMode
revert default value for workbench.tree.expandMode

related to #115873

eamodio/vscode,microsoft/vscode,Microsoft/vscode,eamodio/vscode,Krzysztof-Cieslak/vscode,Microsoft/vscode,eamodio/vscode,Microsoft/vscode,Microsoft/vscode,Microsoft/vscode,eamodio/vscode,Microsoft/vscode,Krzysztof-Cieslak/vscode,eamodio/vscode,eamodio/vscode,microsoft/vscode,Microsoft/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode,eamodio/vscode,Microsoft/vscode,Krzysztof-Cieslak/vscode,eamodio/vscode,microsoft/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode,microsoft/vscode,eamodio/vscode,microsoft/vscode,eamodio/vscode,microsoft/vscode,microsoft/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode,eamodio/vscode,Microsoft/vscode,Krzysztof-Cieslak/vscode,eamodio/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode,eamodio/vscode,eamodio/vscode,Microsoft/vscode,microsoft/vscode,eamodio/vscode,Microsoft/vscode,microsoft/vscode,eamodio/vscode,Krzysztof-Cieslak/vscode,eamodio/vscode,Microsoft/vscode,Microsoft/vscode,Krzysztof-Cieslak/vscode,Microsoft/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode,Microsoft/vscode,Krzysztof-Cieslak/vscode,Krzysztof-Cieslak/vscode,Microsoft/vscode,Microsoft/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode,Krzysztof-Cieslak/vscode,microsoft/vscode,Krzysztof-Cieslak/vscode