py-tifffile: updated to 2021.2.26

2021.2.26
  Pass 4388 tests.
  Squeeze axes of LSM series by default (breaking).
  Add option to preserve single dimensions when reading from series (WIP).
  Do not allow appending to OME-TIFF files.
  Fix reading STK files without name attribute in metadata.
  Make TIFF constants multi-thread safe and pickleable.
  Add detection of NDTiffStorage MajorVersion to read_micromanager_metadata.
  Support ScanImage v4 files in read_scanimage_metadata (not tested).

(adam)