Remove clock resolution page load histograms.

These were temporary metrics intended to understand whether high/low
resolution clocks adversely impact page load metrics. After collecting a few
months of data it was determined that clock resolution doesn't adversely
impact our metrics, and it that these histograms were no longer needed.

BUG=394757

Review-Url: https://codereview.chromium.org/2155143003
Cr-Commit-Position: refs/heads/master@{#406143}