Remove clear /data/local/tmp steps.

Remove clear /data/local/tmp steps.

These were intended to prevent GN and GYP Android bots from stomping on
each other.  Turns out, they don't, even without this... they're writing
most files to completely separate paths:
  - GYP puts most data under $EXTERNAL_STORAGE, generally /sdcard
    and its binaries (libdm.so, libnanobench.so, libskia.so, skia_launcher)
    in /data/local/tmp;
  - GN puts everything under /data/local/tmp, and its binaries (dm, nanobench)
    don't overlap GYP's.

So clearing /data/local/tmp was essentially just removing GN's data; GYP's
data file caching was never affected and can't conflict with GN's.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2340473002

Review-Url: https://codereview.chromium.org/2340473002