Ruby wrapper tests are flaky (on Windows)

[olavloite]

https://github.com/googleapis/go-sql-spanner/actions/runs/20024191956/job/57417679796?pr=674

# Running:

The system cannot find the path specified.
59687
Failed to load a request from log: incompatible marshal file format (can't be read)
	format version 4.8 required; 47.100 given
F..........

Finished in 1.670076s, 6.5865 runs/s, 31.7351 assertions/s.

  1) Failure:
Connection#test_0002_validates read-write transaction lifecycle [spec/spannerlib_ruby_spec.rb:219]:
Expected nil to not be nil.