Bug 1857409 - Port bug 1856100: Remove dead code that handles the removed checkbox from the installer. r=rjl

Differential Revision: https://phabricator.services.mozilla.com/D190258

--HG--
extra : moz-landing-system : lando

mail/installer/windows/nsis/installer.nsi

@@ -597,28 +597,6 @@ Section "-InstallEndCleanup"
   DetailPrint "$(STATUS_CLEANUP)"
   SetDetailsPrint none
 
-  ${Unless} ${Silent}
-    ClearErrors
-    ${MUI_INSTALLOPTIONS_READ} $0 "summary.ini" "Field 4" "State"
-    ${If} "$0" == "1"
-      ${LogHeader} "Setting as the default mail application"
-      ; AddTaskbarSC is needed by MigrateTaskBarShortcut, which is called by
-      ; SetAsDefaultAppUserHKCU. If this is called via ExecCodeSegment,
-      ; MigrateTaskBarShortcut will not see the value of AddTaskbarSC, so we
-      ; send it via a register instead.
-      StrCpy $R0 $AddTaskbarSC
-      ClearErrors
-      ${GetParameters} $0
-      ${GetOptions} "$0" "/UAC:" $0
-      ${If} ${Errors}
-        Call SetAsDefaultMailAppUserHKCU
-      ${Else}
-        GetFunctionAddress $0 SetAsDefaultMailAppUserHKCU
-        UAC::ExecCodeSegment $0
-      ${EndIf}
-    ${EndIf}
-  ${EndUnless}
-
   ; Adds a pinned Task Bar shortcut (see MigrateTaskBarShortcut for details).
   ${MigrateTaskBarShortcut} "$AddTaskbarSC"