Rewrite of '%s' % tuple changes behaviour

[asottile]

(note this is a minimal case, the rule that pyupgrade uses is to avoid 1-ary formats with a single variable on the right hand side since it is not possible to know statically whether that is a format-of-tuple or a format-of-scalar)

before

x = (1,)
print('%s' % x)

$ python3 t.py
1

after

x = (1,)
print(f"{x}")

$ python3 t.py
(1,)

from the testsuite of pyupgrade