Fix outdated comment for readAndWatchFileWithHash

tools/fs/watch.ts

@@ -843,10 +843,6 @@ export function readAndWatchDirectory(
 // Calculating the sha hash can be expensive for large files.  By
 // returning the calculated hash along with the file contents, the
 // hash doesn't need to be calculated again for static files.
-//
-// We only calculate the hash if needed here, so callers must not
-// *rely* on the hash being returned; merely that if the hash is
-// present, it is the correct hash of the contents.
 export function readAndWatchFileWithHash(watchSet: WatchSet, absPath: string) {
   const result: {
     contents: string | Buffer | null;