Use f-strings

[DimitriPapadopoulos]

Change string addition to f-string.

Found using grep '" + ' and grep ' + "'.

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.md
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.11%. Comparing base (029c376) to head (1695018).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3928   +/-   ##
=======================================
  Coverage   93.11%   93.11%           
=======================================
  Files          85       85           
  Lines       11365    11365           
=======================================
  Hits        10582    10582           
  Misses        783      783           

Files with missing lines	Coverage Δ
src/zarr/core/buffer/core.py	82.75% <100.00%> (ø)
src/zarr/core/group.py	94.94% <100.00%> (ø)
src/zarr/registry.py	89.47% <100.00%> (ø)
src/zarr/storage/_fsspec.py	91.32% <100.00%> (ø)
src/zarr/storage/_memory.py	96.74% <100.00%> (ø)
src/zarr/storage/_utils.py	96.25% <100.00%> (ø)
src/zarr/storage/_zip.py	97.68% <100.00%> (ø)
src/zarr/testing/store.py	99.47% <100.00%> (ø)
src/zarr/testing/strategies.py	92.88% <100.00%> (ø)

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