Test Runner: Fix shard parameter script types. The input types are string, not integer. Bug: angleproject:3162 Change-Id: Ib4cac4cc0d4556d607e10fd9b79e36dbed68a39d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2411340 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>