Temp fix till we investigate #55069 making project.ts changes building error free (#55219)

Author: sheetalkamat

src/server/project.ts

@@ -1663,7 +1663,7 @@ export abstract class Project implements LanguageServiceHost, ModuleResolutionHo
         }
     }
 
-    private addMissingFileWatcher(missingFilePath: Path) {
+    private addMissingFileWatcher(missingFilePath: Path): FileWatcher {
         if (isConfiguredProject(this)) {
             // If this file is referenced config file, we are already watching it, no need to watch again
             const configFileExistenceInfo = this.projectService.configFileExistenceInfoCache.get(missingFilePath as string as NormalizedPath);