Fix fs.watch callback type for new @types/node (#54417)

Author: jakebailey

package-lock.json

@@ -812,7 +812,7 @@ function createDirectoryWatcherSupportingRecursive({
 }
 
 /** @internal */
-export type FsWatchCallback = (eventName: "rename" | "change", relativeFileName: string | undefined, modifiedTime?: Date) => void;
+export type FsWatchCallback = (eventName: "rename" | "change", relativeFileName: string | undefined | null, modifiedTime?: Date) => void;
 /** @internal */
 export type FsWatch = (fileOrDirectory: string, entryKind: FileSystemEntryKind, callback: FsWatchCallback, recursive: boolean, fallbackPollingInterval: PollingInterval, fallbackOptions: WatchOptions | undefined) => FileWatcher;
 /** @internal */
@@ -1205,7 +1205,7 @@ export function createSystemWatchFunctions({
             }
         }
 
-        function callbackChangingToMissingFileSystemEntry(event: "rename" | "change", relativeName: string | undefined) {
+        function callbackChangingToMissingFileSystemEntry(event: "rename" | "change", relativeName: string | undefined | null) {
             // In some scenarios, file save operation fires event with fileName.ext~ instead of fileName.ext
             // To ensure we see the file going missing and coming back up (file delete and then recreated)
             // and watches being updated correctly we are calling back with fileName.ext as well as fileName.ext~