listSharedFolders already decoded shared-folder names with
f.opt.Enc.ToStandardName, but listReceivedFiles stored the raw name
returned by the Dropbox API unchanged. Names that require encoding
(e.g. a trailing space, which Dropbox itself rejects, so rclone
stores it as "name␠" via EncodeRightSpace) were therefore shown under
their raw, encoded form for received files instead of being decoded
back to the standard name, and findSharedFile could not resolve such
a file by its standard name.
Apply the same ToStandardName conversion listSharedFolders uses.
