[fuchsia] Replace system-temp with isolated-temp.

This change replaces system-temp with isolated-temp. As system-temp is
now deprecated.

Bug: fuchsia:25081
Change-Id: I4f87b69caa95df7c9809c3eb3d0f7e40ef4cddad
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/266974
Reviewed-by: John Rosasco <rosasco@google.com>
Auto-Submit: Benjamin Wright <benwright@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed