Update createSolutionV2.ps1 (#7374)

Tools/Create-Azure-Sentinel-Solution/V2/createSolutionV2.ps1

@@ -1959,7 +1959,7 @@ foreach ($inputFile in $(Get-ChildItem $path)) {
                                 if ($yaml.relevantTechniques -match ' ') {
                                     $yaml.relevantTechniques = $yaml.relevantTechniques -replace ' ', ''
                                 }
-                                $alertRule | Add-Member -NotePropertyName techniques -NotePropertyValue ($yaml.relevantTechniques | ForEach-Object { ($_ -split "\.")[0] }) # Add relevantTechniques property if exists
+                                $alertRule | Add-Member -NotePropertyName techniques -NotePropertyValue ([array]($yaml.relevantTechniques | ForEach-Object { ($_ -split "\.")[0] })) # Add relevantTechniques property if exists
                             }
                            
                             $alertRule.description = $yaml.description.TrimEnd() #remove newlines at the end of the string if there are any.