With ag/20611145, the dir size is not uint32max by default. Update the
value in the test accordingly.
(The test was not discovered in CI because gotestrunner
runs the tests using `-test.short` flag, and skips this test)
Test: go test ./third_party/zip -run TestZip64P7ZipRecords
Change-Id: I47885f23fe32ff5ed30c44d52561cd11d59020ec