[tools/perf] Update link to story disabling documentation

The link from the expectations.config file itself was outdated.

Bug: 842232
Change-Id: I8260c338b1cc176136cf24bea0adc921b442a87b
Reviewed-on: https://chromium-review.googlesource.com/1102323
Commit-Queue: Charlie Andrews <charliea@chromium.org>
Reviewed-by: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567726}

tools/perf/expectations.config

 # Test Expectation file for telemetry tests.
 # Instructions of how to use this file:
-# https://chromium.googlesource.com/chromium/src/+/master/docs/speed/perf_bot_sheriffing.md#Disabling-Telemetry-Tests
+# https://chromium.googlesource.com/chromium/src/+/master/docs/speed/bot_health_sheriffing/how_to_disable_a_story.md
 
 # tags: All Android_Go Android_One Android_Svelte Android_Low_End
 # tags: Android_Webview Android_but_not_webview Mac Win Linux