Increases the max number of cached packages.

R=iannucci, vadimsh

Bug: 1003774
Change-Id: I489bca5e6ede4dfb28662b2ba640c972da5afb87
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1806137
Auto-Submit: Andrii Shyshkalov <tandrii@google.com>
Reviewed-by: Vadim Shtayura <vadimsh@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@google.com>