O365 Powershell script to Delete user from all Site Collection

Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue

Function DeleteUserFromAllSites([string]$WebAppURL, [string]$UserAccount, [bool]$ScanOnly)
{
   
   #Get the web application
   $WebApp = Get-SPWebApplication $WebAppURL
   
   #Loop through each site collection
   foreach ($Site in $WebApp.Sites)
   {
    try
           {
      $ErrorActionPreference = "Stop"
      #Try to get the User
      $User = $Site.RootWeb.SiteUsers | Where-Object {$_.LoginName -eq $UserAccount}
     
      #If user account found
      if($User -ne $null)
      {
       if($ScanOnly -eq $true)
       {
        Write-Host "Found user on: $($site.Rootweb.URL)"
       }
       else
       {
        #Remove the User from site collection
        $Site.RootWeb.SiteUsers.Remove($UserAccount)
        Write-Host "User Deleted from: $($site.Rootweb.URL)"
       }
      }
   
     }
    catch
           {
      #Write error message on screen and to a LOG file
               write-host "Error Deleting user from site collection: $($site.rootweb.url)`n" $_.Exception.Message
      $_.Exception.Message >> "d:\error.log"
           }
          finally
          {
              $ErrorActionPreference = "Continue"
                                $site.Dispose()
          }
   }
}

#Call the function
DeleteUserFromAllSites "http://sharepoint.crescent.com" "global\davep" $true