CLN: replace %s syntax with .format in tests.io.formats/json/sas

[AaronCritchley]

• Progress towards CLN: replace %s formatting syntax with .format #16130
• tests passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff

[codecov]

Codecov Report

Merging #18351 into master will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #18351      +/-   ##
==========================================
- Coverage   91.38%   91.34%   -0.05%     
==========================================
  Files         164      164              
  Lines       49790    49790              
==========================================
- Hits        45501    45480      -21     
- Misses       4289     4310      +21

Flag	Coverage Δ
#multiple	89.14% <ø> (-0.03%)	⬇️
#single	39.49% <ø> (-0.07%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/plotting/_converter.py	63.44% <0%> (-1.82%)	⬇️
pandas/core/frame.py	97.8% <0%> (-0.1%)	⬇️

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[jreback]

thanks!