crostini: Remove redundant code

Test: CQ
Bug: chromium:1064512
Change-Id: Ie504706d4bb900638ba4ba4772dec7cfa79b8fb6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2259752
Commit-Queue: David Munro <davidmunro@google.com>
Auto-Submit: David Munro <davidmunro@google.com>
Reviewed-by: Jason Lin <lxj@google.com>
Cr-Commit-Position: refs/heads/master@{#781257}

chrome/browser/chromeos/crostini/crostini_manager.cc

@@ -2547,9 +2547,6 @@ void CrostiniManager::OnStartLxdProgress(
   CrostiniResult result = CrostiniResult::UNKNOWN_ERROR;
 
   switch (signal.status()) {
-    case vm_tools::cicerone::StartLxdProgressSignal::UNKNOWN:
-      result = CrostiniResult::UNKNOWN_ERROR;
-      break;
     case vm_tools::cicerone::StartLxdProgressSignal::STARTED:
       result = CrostiniResult::SUCCESS;
       break;
@@ -2561,7 +2558,6 @@ void CrostiniManager::OnStartLxdProgress(
       result = CrostiniResult::START_LXD_FAILED;
       break;
     default:
-      result = CrostiniResult::UNKNOWN_ERROR;
       break;
   }