Format B now default, Google Drive saving fix

This release fixes an issue with Google Drive vaults not saving correctly (duplicated "Untitled" files in Google Drive). These files do contain partially-valid vaults, so do not delete them if you have saved vital information there since `v2.19.0`` was released. We sincerely apologise for the inconvenience here.

Please note that this version changes the default vault format type to B instead of A. This is only relevant for new vaults (existing vaults continue to use their original vault format until upgraded). Format B has been supported for a longer time now - it is recommended to upgrade for performance and stability.