LSP: Update config for Dart

rootFileIndicationNames are not needed.

addons/lspclient/settings.json

@@ -35,7 +35,6 @@
         "dart": {
             "command": ["dart", "analysis_server.dart.snapshot", "--lsp"],
             "url": "https://github.com/dart-lang/sdk/blob/master/pkg/analysis_server/tool",
-            "rootIndicationFileNames": ["pubspec.yaml"],
             "highlightingModeRegex": "^Dart$",
             "initializationOptions": {
                 "onlyAnalyzeProjectsWithOpenFiles": true