[roll] Roll fuchsia [testsharder] Lower max runs for multiplied tests

Multiplying a test many times can cause issues processing and uploading
the resulting shard's logs and test results, because they might be
massive. This is especially bad for automatically multiplied tests,
where the fact that the builder is running any multiplied shards is
generally (as it should be) completely opaque to the CL owner. For
example: https://ci.chromium.org/b/8860625698851501456

To make such processing failures less common, reduce the maximum number
of test runs that testsharder will calculate from 2000 to 1000. This
shouldn't have much user-facing impact, as the limit doesn't apply to
user-specificied run counts. For example, "MULTIPLY: foo_test: 5000"
will still run foo_test 5000 times, but "MULTIPLY: foo_test" will never
run foo_test more than 1000 times now.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/464614
Original-Revision: 3e8653c84d3a3ae72376ad9dbdfb97af50fec705
GitOrigin-RevId: d83dcd2489a368060a1921aee658b9e5d181f3f0
Change-Id: Ic480a49d526d7a25909ffae6ac363667e9a33022