Fix ConciseView to not show the line information within the error messages (#11952)

src/System.Management.Automation/FormatAndOutput/DefaultFormatters/PowerShellCore_format_ps1xml.cs

@@ -1100,7 +1100,8 @@ namespace System.Management.Automation.Runspaces
                                                 $offsetInLine = 0
                                             }
                                             else {
-                                                $positionMessage = $myinv.PositionMessage.Split($newline)
+                                                # use newline char instead of $newline because that is what is in the message
+                                                $positionMessage = $myinv.PositionMessage.Split(""`n"")
                                                 $line = $positionMessage[1].Substring(1) # skip the '+' at the start
                                                 $highlightLine = $positionMessage[$positionMessage.Count - 1].Substring(1)
                                                 $offsetLength = $highlightLine.Trim().Length

test/powershell/engine/Formatting/ErrorView.Tests.ps1

@@ -99,6 +99,12 @@ Describe 'Tests for $ErrorView' -Tag CI {
             $e = { throw "$msg" } | Should -Throw $msg -PassThru | Out-String
             $e | Should -BeLike "*$msg*"
         }
+
+        It "Position message does not contain line information" {
+
+            $e = & "$PSHOME/pwsh" -noprofile -command "foreach abc" | Out-String
+            $e | Should -Not -BeLike "*At line*"
+        }
     }
 
     Context 'NormalView tests' {