fix: tests should match stderr for verbose output

cmd/car/testdata/script/create-extract.txt

@@ -1,7 +1,7 @@
 car create --file=out.car foo.txt bar.txt
 mkdir out
 car extract -v -f out.car out
-stdout -count=2 'txt$'
+stderr -count=2 'txt$'
 stderr -count=1 '^extracted 2 file\(s\)$'
 car create --file=out2.car out/foo.txt out/bar.txt
 cmp out.car out2.car