[telemetry] Fix perf/run_tests after r239318.
[telemetry] Fix perf/run_tests after r239318.

perf_tools no longer exists, so remove the import.
Previously, importing perf_tools would implicitly add telemetry to our sys.path, but now we have to do it explicitly. This is a Good Thing.

BUG=311380
TEST=tools/telemetry/run_tests; tools/perf/run_tests.
TBR=tonyg

Review URL: https://codereview.chromium.org/108193010

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@240459 0039d316-1c4b-4281-b951-d872f2087c98

SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult-csm,benschmaus/catapult,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,catapult-project/catapult,SummerLW/Perf-Insight-Report,SummerLW/Perf-Insight-Report,sahiljain/catapult,catapult-project/catapult-csm,sahiljain/catapult,sahiljain/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult,benschmaus/catapult,SummerLW/Perf-Insight-Report,catapult-project/catapult,catapult-project/catapult-csm,benschmaus/catapult,sahiljain/catapult,sahiljain/catapult,benschmaus/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult-csm